Is Lollipop limited to two users per device? This is very nearly a duplicate of "Is Asus Memo Pad 8 limited to 2 users?," but I am having the same issue on a Moto G (1st gen). 

Is Lollipop limited to two users per device?

When I tap on "+ Add User" nothing happens once I have two users on the device.
It aint limited to 2 users. If you are rooted, you can use the following shell commands to add/remove the number of users in the device.   

adb shell # 
su
mount -o rw,remount /system
echo fw.max_users=4 &gt;&gt; /system/build.prop #4 denotes the number of users you want to have.
exit
reboot #to apply the changes


hope it helps someone