For those facing the same issue, we have resolved it and it looks like Square Support is on the ball with this one. It just takes a little bit of fine toothing to make sure all the credentials are in the right place.
Alright, for iOS, many of us in the past have used older Bundle IDs’ and this has been fine but with (I assume) recent updates to the SDK’s, the Bundle ID for both Android and iOS must be what is on the App Stores. They will usually match if you are using React Native. Ensure that the Bundle ID is correct and that will be the most common fault for iOS.
For Android (and as its been posted many times and was also the case here), go to your Google Play developer console → Go to your App → Protected with Play → Play Store Protection → Manage Play App Signing → Find your SHA-256 Certificate and use that without : and lower case (which the Square Console requires you to do anyways). Also ensure the Package name is properly matched with what Google Play has.
Finally, go BACK to your application and you want to restart all of your hardware so it forces it to reconnect with Square.
This should resolve your issues. Let me know if this helps.