Try changing your security rules to the following:
rules_version = '2'; service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read, write: if true; } } }

You can make your rule as per below. It is also secure
rules_version = '2'; service cloud.firestore { match /databases/{database}/documents { match /{document=**} { allow read, write: if request.auth != null; } } }