Source: iOS devices APN certificate request error when signing to Intune SCCM 2012 R2
This is a fix to the issue – Purge APNs certificate data in SCCM SQL Database In Configuration Manager, disable iOS inside of the Windows Intune Connector. Go to “Administration > Cloud Services” Right click the Intune subscription in the right pane and select “Properties” to get a popup window. On the “iOS” tab,