S4 CM 12.1 Problem with GApps I've just installed cm-12.1-20151129-NIGHTLY-jfltexx on my S4 (i9505) and Open GApps 5.1 Arm nano 20151129. The setup wizard had few errors (Google play services stopped working) and after setting it up the gapps instead of showing icon and name are showing package name and default icon, when trying to run it, it says "this app is not installed on your phone" or something like this. Every now and then message pops up saying "Google play services has been stopped". Also NFC is not working (idk but it's probably something to do with the ROM)

What am I doing wrong? Wrong GApps / ROM combo?
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..!