"app name" is no longer available message

Hi there;

We are the developers of an enterprise iOS application for internal distribution.

Since a few hours, we start to receive "(app name) is no longer available" error message and can't open the app.

When I further investigated, the company certificate in which I have trusted in General/Device Management / Enterprise Apps is no longer available/deleted.

But the certificate is still valid,

Do you have any advice for an immediate solution?