PoGo uses google’s SafetyNet for protection, so you need to fulfill it requirements in order to login. I haven’t been able to login for couple of months since SafetyNet update which started to check for phone’s bootloader unlock status. If your bootloader is unlocked(and it should be, otherwise you can’t install CM), SafetyNet check fails even if you removed root. There was a solution – a patch for bootloader, but it should be compiled for each phone individually, and no one did it for Xiaomi Mi4c afaik.
Maybe now bootloader check for Mi4c have been bypassed already, but the problem is still here cause google can patch SafetyNet on the fly, so it’s just a neverending cat and mouse game with more and more challenging bypassing conditions, so I got tired of this and chose to have CM, root, Xposed and other features rather than sit on stock MIUI to play one game.
If you are still willing to play PoGo, you should search for SafetyNet current bypass methods.