I wanted to update an application in the Google Play Store, and when clicking "Update" I got an error message:
Error retrieving information from server [RPC:S-7:AEC-7 ...]
There is a thread on XDA developers about this issue which recommends to clear the cache or log out and login into google apps - but that did not help here. Re-flashing Open GApps to the latest version did also not help.
I'm using Cyanogenmod 13, and I played around with the app permissions lately. Resetting them to the default state and rebooting made the play store downloads work again: Settings -> Apps -> ⠇ -> Reset app settings.