I used the official Patreon plugin on my WordPress site and almost every user has been able to access my posts correctly. One user who is above the tier limit receives an error in every browser he tries:
Sorry. Login aborted due to an API error. - Patreon returned: invalid_grant
I have searched here and the web and can find no answer. Any help is appreciated.
Checking that you have your account credentials entered correctly would be the first thing to do - you need to make sure you not copy/pasted any spaces at start or at the end by mistake.
You also have to have all the access details - from client id to creator’s access token.
After this, please make sure that you clear your entire cache. If your host has caching server-side, you should also clear that. Also, if you are using WPEngine, ask them to exclude patreon_nonce cookie from their caching.
Then having one user clear all cookies for your website’s domain, and Patreon and then logging in with Patreon should tell us if there is something wrong with your setup or not.