I am trying to only allow reads coins's documents if the user's uid matches the userId (encircled in red).

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    
    match /{document=**} {
        allow read, write: if false;
    }
    
    match /coins/{coinId} {
        allow read: if request.auth != null && resource.data.userId == request.auth.uid;
        allow write: if request.auth != null;
    }
  }
}

This rule returns an error in the console when I log into my account. And no data is displayed. Uncaught error in snapshot listener: FirebaseError: Missing or insufficient permissions.

Based on everything I've read here it seems like the following code should work, but it doesn't.