Q: Can't update or download apps after getting iOS 10

Same Here, if I figure it out I'll let you know

Only way I was able to fix was to go into iPhone settings and "Erase All Content and Settings"

After that I restored from my most recent backup (didnt matter the last backup was on iOS9) and that fixed the issue once the restore was complete.

This worked for me.  First I tried resetting all settings but no dice.  Had to erase everything and restore from a backup.