For those of you who enabled Google Play App Signing, you'll also have to add the SHA-1 key from the "App Signing Certificate" to your Firebase console and use the updated google-services.json in order for the invite to work on apps launched to the Google Play Store.
Steps to locate the SHA-1 key:
1) Go to your Google Play Console
2) Select the targeting app
3) Go to "App signing" under "Release management"
4) The SHA-1 key can be found under "App Signing Certificate"
It took me many hours to resolve the issue and I hope this can help someone who runs into the same issue.