Hi Fabrizio,
Your Azure for Students subscription restricts which regions you can create storage account in. Please look further into the error message and you should see a list of regions you are permitted to use. You may need to click on the Raw error tab and scroll down to find the specific message, or click on Activity log blade of the resource group and click into the various errors and look at the JSON.
For example, it should have text similar to "You can create resources in the following regions <region1>, <region2>, <region3>, <region4>, <region5> only."
Once you know the list of regions, try creating your storage account in one of the permitted regions and it will likely succeed.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP