Troubleshooting steps for iOS push notifications certificate issues
This error means that the certificates uploaded for your iOS app in Settings > App & Sites are invalid. These can be invalid for a number of reasons:
You could be using the incorrect type of file/cert
You may have uploaded a cert for a different app
A development cert could be in the place of the enterprise cert or vice a versa
The certificates could be out of date
If you encounter such an error read the iOS push notifications page and double check you have uploaded the correct certificates.