iOS device won't allow to open the app with distribution certificate not expired nor revoked

Our enterprise app was distributed through Fabric Crashlytics Beta but after a year the app won't open from the device. When you tap the icon it will just close. It can't be download also.

The distribution certificate was not expired nor revoked.

And releasing a build with a new generated certificate fixed the issue but the cause is still unknown.

The certificate is valid for 3 years, but the provisioning profile you used to build the app with is valid for 1 year at most. You can push a new provisioning profile to the devices without having to re-build the app, but without a non-expired provisioning profile that is valid for the app's bundle ID and the certificate used to sign it, the app will refuse to run.

Long story short, if you are doing enterprise distributions, you will need to push out a provisioning profile (either through mobile device management [MDM] or by building the app again with a new provisioning profile [the profile is bundled with the ipa when you package the app]) at least once a year. Then once every 3 years, you will need to get a new certificate, generate a new profile for that certificate, and build and deploy a new binary that has been signed with the new cert.