Login Error on New Site

I opened my site up to my patrons to check for errors and I got one from a patron after they click from Patreon back to my site:

I get an error when I hit the ‘unlock with patreon’ button. It’s a blank white page with this string of text on it: {“error”:“invalid_request”,“error_description”:“Mismatching redirect URI.”,“state”:“eyJmaW5hbF9yZWRpcmVjdF91cmkiOiJodHRwczpcL1wvdGNyb3NzLnVzXC9wYXRyZW9uLXNpc3Rlci1zaXRlXC8ifQ==”}

WP 6.0.2 with PHP 8.0.2
Patreon WordPress 1.8.4 with API v2

Does your site use mixed http:// and https:// urls?

Not that I’m aware. It’s all https when I’m on it.

But does your site allow your site to be loaded over http:// instead of redirecting it to https://? Your users may be coming from old http:// links that they find on the Internet etc and then they may end up trying unlock or login via Patreon over http://. This would cause redirect error if your redirect url is saved as https:// in your app settings at Patreon.

How do I check that?

Just type the url of a post at your site with http:// and load the page. If it does not redirect to https:// and reloads the page over https://, then you are using mixed urls.

It redirected to https://.

Can you check your redirect url that is saved in the apps page and compare it to the redirect url shown in Patreon Settings → Connection menu at your WP admin?

In the apps page on Patreon? I looked and it’s only listing Vimeo. Not sure what to do at this point if Patreon is supposed to be there. On the settings on my WP admin it’s https: