I don’t offer private support actually.
When you set user-agent auth in Bubble API Connector, you first need to “iniialize” the auth. This is what the message at the bottom tell you: Create a page with a button with action set to login with a social network and click on preview. Authenticate to your SF account to initialize API Connector auth. Once it’s done, add new API Calls that will use this auth. Take note that API Connector with not keep your connection alive and once the access token is expired, you need to reauthenticate again. However, Bubble will keep access_token alive when needed using the refresh token for your users.

However, like I said, I think you should consider to use the manual auth process instead and set API Connector to none/self-handled auth.