When you log in as a Patreon user through OAuth the Access Token and Refresh Token for you for that client are refreshed, and since your Creator's Access Token and Creator's Refresh Token are just standard tokens for that client the old tokens (what you’ve configured in your control panel) are no longer valid. Therefore, you must not log in to your Patreon OAuth integrated website with the Patreon creator’s account of the OAuth client, because it will refresh the tokens.
If you want to test your website that uses Patreon OAuth then you should create a new Patreon account specifically for testing – which is beneficial anyway, since a creator cannot be a patron of a campaign, so by logging in with your creator account you’re not accurately testing the experience of your patrons.