Lets try this:
Just delete whatever app you have at Patreon app listing page below.
Then, create a new one manually. Copy/paste the redirect uri that you see in Patreon plugin settings when you click ‘Connection details’ at your WP site to the ‘redirect uri’ field’. And choose ‘v2’ as version.
After manually creating this client, copy/paste the 4 connection details it provides to relevant input details to ‘Connection details’ part in your Patreon plugin settings at your site. Then save.
After that, visit a post editor page to edit any post (or post a new one) and see if you can see your Patreon tiers loaded in the ‘Patreon level’ metabox.