Can't enable Amplify Studio for my backend

After using Amplify Studio for several months with my account on the free-tier, and having only one backend in the us-east-1 region, suddenly I can no longer use Amplify Studio. No matter how many times I try to click the "enable" button, it doesn't activate, and the only response I get is an error message in Chrome developer tools saying "No resource with the given identifier found" when I try to access the URL "https://prod.us-east-1.appstate.amplifyapp.com/AppState?appId=d5bu556qepejs". I use Amplify for several services (auth, storage, datastore, predictions, and API), and I don't understand why I can't use Amplify Studio anymore, as I believe I haven't exceeded quotas, and my usage is still below the free-tier limits. What could be happening? Any ideas?