Well, I’m experiencing a similar issue: Notifications not working in AAB build: Fetching the token failed: FIS_AUTH_ERROR. Code: E_REGISTRATION_FAILED. - Help: Expo SDK - Forums, but in your case I guess you should use the GCP API key that was auto-generated by Firebase (top one in your screenshot). That one should match the one in your downloaded google-services.json.
edit: If you only have 1 api key (which you do) that one should be in the google-services.json is my guess.