Installing/updating apps over mobile data
I think I found it, as I had the same problem:


In the Settings go to Mobile Data.
Scroll down to item "Media" and tap it.
Scroll down and see if "Limit background data" is checked. If so, uncheck


This was the cause in my case, because for the Play Store app the same setting was not active. The problem with Android in this situation is, that there is a global setting "Limit background data" and there's a per app setting. Unchecking the global setting does not uncheck the per app setting. Doh!