Hi
Thanks for reaching out to Microsoft Q&A.
I could see an answer which states to remove cookies and you have stated that you added them in the settings. However, I see similar question to yours with a useful answer, pls check the link below.
[https://answers.microsoft.com/en-us/msteams/forum/all/aadsts900561-the-endpoint-only-accepts-post/d89a7d5a-6695-43a9-8702-92d50a849400
Please Upvote and Accept as answer if the reply was helpful, this will be helpful to other community members.