Here's the reply from Patreon Staff, essentially saying the issue is on itchio side. Any ideas?
I see. Thanks very much for elaborating! That does sound like it might be it.
If that's it, it's very weird though, that the dev from Patreon wouldn't put 1 and 1 together. Like that them taking off an API and users coming in to say their API access isn't working anymore is connected.
I asked them about the legacy API, waiting for a response.