Keep getting error codes (400 or 411) on send http request under microsoft groups in power automate

Question

Keep getting error codes (400 or 411) on send http request under microsoft groups in power automate

Glen Raudanskis 0

I am trying to use power automate to create a flow that updates a group calendar when a new sharepoint list item is created. I've managed to make it so that when a new item is created, a new event is created in the calendar. I used the 'Create a group event (v2)' action to do this. The last step I want to do is make it so that the event in the calendar changes categories to make it a different colour. Unfortunately, the parameters in the 'Create a group event (v2)' action do not support this. So instead, I was trying to use the 'send http request v2' under office 365 groups to do this but I keep running into the error code '411 LengthRequiered' even though I have text in the body. I found a link that says I can do this but no matter what I try it doesn't work.

https://learn.microsoft.com/en-us/graph/api/event-update?view=graph-rest-1.0&tabs=http

I've tried adding in a custom header that specifies the content length but that didn't work either.

I also found this link which seems to maybe say that this is an issue that microsoft is working to resolve right now but I'm not sure if it means this directly. Also, this issue was from several weeks ago and it says it should've been fixed by eod from the day it was posted.

Here are the last two codes I was using (i removed my calendar id for privacy):

{ "type": "OpenApiConnection", "inputs": { "parameters": { "Uri": "https://graph.microsoft.com/v1.0/groups/(group id)/events/@{outputs('FilmingEvent')?['body/id']}", "Method": "PATCH", "CustomHeader1": "Content-Length: @{outputs('clfilming')}", "Body": "{"categories":["Red category"]}", "ContentType": "application/json" }, "host": { "apiId": "/providers/Microsoft.PowerApps/apis/shared_office365groups", "connection": "shared_office365groups", "operationId": "HttpRequestV2" } }, "runAfter": { "FilmingEvent": [ "Succeeded" ] }, "metadata": { "operationMetadataId": "0a13ae12-3700-478e-801f-c417cca31be2" } }

Can anyone help me understand if this is even something I can do? Is it broken right now? Is there a way for me to know when it will be fixed?

Glen Raudanskis 0 Reputation points

2025-08-11T15:50:45.9233333+00:00

Forgot to include the second link:
https://admin.powerplatform.microsoft.com/support/knownissues/5344962

3 answers

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Glen Raudanskis 0 Reputation points

2025-08-11T15:50:45.9233333+00:00

Forgot to include the second link:
https://admin.powerplatform.microsoft.com/support/knownissues/5344962

Answer 1

Michael Taylor 60,601

It is unclear to me if you're explicitly calling the API directly or using one of the builtin approaches. In general content length is auto-calculated based upon the body. But if you're manually building up the request packe then this is on you.

Your calculation looks wrong to me. It is using @{outputs('clfilming')}. I don't know what that is but an output seems after the fact. Also it would need to be an integral value. The content length is the length of the body so in your sample the value should just be "{"categories":["Red category"]}" length or 32 (?). Note that your JSON has double quotes and is itself wrapped in double quotes so I'm not sure if that is a display issue or your JSON may not be correct.

I would try hard coding the length to the correct value for the body you're sending as a test. If that works then your content-length calculation is wrong. If it generates a 400 then your body is malformed and probably the double quotes. You likely need to use " instead of double quotes inside the body.

Glen Raudanskis 0 Reputation points

2025-08-11T16:29:30.8733333+00:00

Thanks for looking into this Michael. I was using a more complicated way after multiple failed attempts using a straight forward strategy like you suggested. I just changed the code and hard coded some things like you said but I'm still running into error 411 LengthRequired. I am trying to use one of the built in approaches. I've also read online that "Office 365 Groups → Send an HTTP request only supports a subset of Graph endpoints for Groups (members, drives, conversations, etc.). It does not support the calendar/events endpoints". I don't know if this is true based on the other things I've read and seen. I've uploaded a picture of my flow in case this helps.
Michael Taylor 60,601 Reputation points

2025-08-11T16:35:51.4433333+00:00

You know, looking at your raw request, the content type is wrong. The HTTP header is Content-Type, not ContentType. As I mentioned, normally you use an existing component/tool to make REST calls and it is responsible for taking the body and setting the HTTP headers. If you're building it by hand you're on your own.

Try setting the Content-Type header to be application/json. I wonder if the API is not getting a content type and so it is not sure how to process the body.

Another suggestion I'd have is to use Graph Explorer or another tool to generate a valid API request. Then take a look at the raw request that is sent and use that as a basis for building your own raw request if you need that behavior. But ideally you should use the HTTP Action of PA as that will handle a lot of the details for you.
Glen Raudanskis 0 Reputation points

2025-08-11T16:43:09.0233333+00:00

I think that's just how the code writes itself. If you look at the picture I uploaded on the bottom left, it does say Content-Type and application/json.

I'm confused about your second suggestion though...I do agree that simply using the http request of PA is the way it should be done but I'm starting to think the endpoint might just not be supported
Michael Taylor 60,601 Reputation points

2025-08-11T17:14:57.9266667+00:00

Can you share the image again? I don't see any images in your responses. The first link was to the documentation and the second link is to a signin page.

The REST API supports the call, based upon the docs you linked, so PA should have no issues calling it. If the data you're sending is bad then I'd expect a 400. If the API wasn't supported then I'd expect a 404. A 422 indicates a bad HTTP header.

Can you capture the raw HTTP response going across the wire (maybe using Fiddler or Wireshark)? This would help confirm what is actually being sent. I'm assuming you're running PA locally and that it is making the calls from your network out. But I don't run PA so I cannot confirm.
Glen Raudanskis 0 Reputation points

2025-08-11T17:19:43.4633333+00:00
Michael Taylor 60,601 Reputation points

2025-08-11T18:36:52.6+00:00

Thanks! Since you're using the Send action and the content type is JSON it should be able to figure out the content length automatically. If you don't specify the HTTP header specifically, what error are you getting?

I'm assuming you're adding the custom header using the Advanced options so you can ensure it is formatted the way the task requires.

I'm starting to understand now what you meant when you originally said Office 365 Groups didn't work. Based upon the post here, that isn't supported. I don't know why as it is just a REST API call. The link was talking about authentication which doesn't seem to line up with your scenario. Also, if you successfully made a call to create the event and now you're just updating it then I would expect it to work.
Glen Raudanskis 0 Reputation points

2025-08-11T20:07:56.1933333+00:00

I still get the same 411 error which is weird. I saw that post too and know it was about something else but still makes me believe that this action isnt supported. For now, I just switched to a shared mailbox calendar.

Answer 2

Hi,

I'm Sumit, here to help with your query on the Microsoft Q&A forums.

Apologies for any inconvenience you are experiencing. I am happy to help you today.

The Microsoft Q&A platform does not currently provide support for Power Platform–related queries. For the best assistance, please post your question on the official Power Platform Community forum: https://community.powerplatform.com/

This will connect you directly with experts and community members who specialize in Power Platform.\

I hope you find this information useful. If you have any more questions, don't hesitate to reach out, otherwise, click Accept solution to close it. Wishing you good luck!

Answer 3

Sumit D - IA 132.1K Independent Advisor

Hi Glen, as I said you would surely get a better answer at the Power Automate community since the question more of relates to that.

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Keep getting error codes (400 or 411) on send http request under microsoft groups in power automate

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