https://itch.io/api/1/KEY/me
replacing the "KEY" with oauth key and request, it will now redirects you to https://api.itch.io/me and show error:

{"errors":["invalid api version: expected 1"],"details":"The API endpoint you tried to access is not available on version of the API you requested "}

Issue was related to our migration to Cloudflare. The issue should be fixed now and those API endpoints working as expected.

the expected behavior is that it returns a json described in
https://itch.io/docs/api/serverside#reference/profileme-httpsitchioapi1keyme
This issue has caused the game Among Us unable to login through eos gateway

Sounds like the new DDoS mitigation measures put in place a few hours ago might have side effects. I've let our admins know.