
That’s because the app store is built using expired enterprise certificates, and Apple will revoke these regularly. TopStore is an unofficial app, and Apple is not fond of these. If it isn’t, the other way to fix it is to delete it and reinstall it.

Open TopStore by tapping the icon on your home screen.Using TopStore is no harder than any other app store: Go into Profiles & Device Management and tap on the app profile.First, open Settings and go to General.When you see the app icon on your home screen, TopStore is installed, But, you can’t use it yet.Using the Safari browser on your device, download the configuration profile for TopStore.

Although you can’t get TopStore in the official appstore, you can download the configuration profiles straight onto your device.
