S4 CM 12.1 Problem with GApps
maybe there is bug in the NIGHTLY edition so you have two options - 

1> download the Latest release  2015-11-17 and install it.
http://download.cyanogenmod.org/get/jfltexx-snapshot.zip

2> an alternative is to install GApps tk_gapps-modular-pico-5.1.1-20150920 (which I am using now on my device)
using this link https://www.androidfilehost.com/?fid=24052804347819443

download zip and install.

this may help! good luck..!