hey @User . 401 means that the session has expired. The diff in versions is: - In 2.3, we used a slightly inefficient method to handling refresh tokens. - In 2.4, we optimised the refresh token handling, but made it such that if a refresh token was issued in 2.3, that would continue to work and on next refresh, the refresh token issued would use the optimised way. - In 2.5, we stopped supporting the refresh tokens from <= 2.3. If you have users in production who are logged into sessions created via the 2.3 core, and you want to migrate to 2.5, you should keep running 2.4 until you are sure all your user's sessions have been refreshed at least once, and then move to 2.5. ------------------- If you never used 2.3 in the first place, then I would need more info to help find the issue. You can find more info in the logs of the core. If you are using docker, then you can run

docker logs

to find them, else, without docker, you can find a log folder in the location where you have installed supertokens.