Starting around 2020-07-27 16:00 UTC, part (or all) of my application does not run properly due to missing connectors.
Certain custom connectors were offline and are in the process of being restored. Application functionality that uses these specific custom connectors will fail. This failure may be limited to the specific part of a Power App that uses a specific connector. If the entire application is based on these custom connectors, it will not work.
How to fix this issue
We are in the process of restoring custom connectors. When all of the custom connectors are restored, application will start working properly.
Alternatively as an immediate fix, you may open the application and delete the custom connector as a resource and then re-add it and then republish your application. This will immediately fix the application.