Array ( [error] => invalid_grant [error_description] => Bad Request )

[Grafidea]

I get errors like this from time to time. Is this some error in the system?

[ThunderBlue]

I am not sure, but it seems to be a problem with the verification code.

[SeNioR-]

In the OAuth2 spec, "invalid_grant" is sort of a catch-all for all errors related to invalid/expired/revoked tokens (auth grant or refresh token).

Maybe the user revoked access to the application and later tried to log in without permission.