Hello,
On our CRM sandbox environment, we've done a number of customisations on the Customer Service and Sales Hub apps (unified interface). Since a couple of days, we're not able to access these any longer.

We think this might have been caused, by some modifications on the apps itself, but we're not certain. The problem does not persist on the Customer service and Sales app (web)
The issue is not related to security roles. The user accounts have the same role as required for the app and also have got System administrator and System customiser enabled.
Since we're unable to access the app designer for the apps - what can we do?
Thanks in advance.
Best regards,
Neal Jacobs