I recently looked into a case in which Patreon WordPress was failing to unlock content for qualifying patrons.
The web host informed the site owner that the process was failing due to a cookie named ‘patreon_cookie’.
Except that cookie was removed from the plugin ~2 years ago. Meaning that the plugin version at the site is likely extremely old.
In order to avoid such situations, always try to make sure that you are running the latest version of the plugin. Otherwise you may encounter issues that were solved long before.