Our development team was notified that there was an issue when authenticating using an access token. The bug was only in version 4.2.1 and resulted in an error “Invalid_token” when trying to authenticate.
The bug also caused an issue with a sister plugin called “Simple Single Sign On” found on the WordPress repo at https://wordpress.org/plugins/single-sign-on-client/. The error would display as “User Mismatch” because while the user could authenticate at first to know there was a user available for SSO, the user info returned was an error without a check.
A bug fix has been released of WordPress OAuth Server and we will be pushing an update to SImple Single Sign-On here shortly that provides additional checks during an SSO event.
The latest version can be downloaded or updated with a valid license. If you need the latest copy and would like to download it, enjoy 30% of the PRO version by visiting https://wp-oauth.com/downloads/wp-oauth-server/?discount=OAUTH2022
Please contact support for any issues you may be having.