AADSTS900561: The endpoint only accepts POST requests. Received a GET request.

Dear Seima Nur,

Good Day! Thank you for posting to the Microsoft Community. We are happy to help you.

Based on your description, I understand that you have a query "AADSTS900561: The endpoint only accepts POST requests. Received a GET request."

I'm sorry to hear that you're having trouble logging into your account. The error message you're seeing indicates that the endpoint you're trying to access only accepts POST requests, but you're sending a GET request instead. The most common reason for this issue is that you might have multiple sessions on various tabs on your browser and you logged out and logged into some other account causing an invalid token issue Or, somehow the browser has sent an HTTP GET with an invalid query, instead of an HTTP POST as required by the server. This could be due to a number of reasons, such as an issue with your browser or network connection. If the issue persists after closing all other sessions;

1. Which browser are you using? Have you tried different browser to check if it works? Try opening a Private/Incognito window in your Browser (or clear the cache)
2. Have you tried adding the https://login.microsoftonline.com to your list of trusted sites?
3. Have you tried opening the Run Dialog and type inetcpl.cpl > Internet Options > Privacy tab > Under Settings > Sites > Per Site Privacy Actions > Enter the Login URL you are having issues (https://login.microsoftonline.com > Click Allow and OK

We look forward to hearing from you; Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. Thank you for your cooperation.

Sincerely,

De Paul | Microsoft Community Moderator