URL not found on Google Play app when signed in as internal app tester

For anyone still running into this, make sure to go to Settings -> Internal App Sharing and accept the terms. The Play Store link started working instantly after doing so.

May be your IARC Content Ratings has not been accepted yet. Just wait for one or two more days. It will be accepted and app will be available on play store. If it doesn't create a new IARC Ratings.