Did you do a local backup before messing with the world of Roms
if not then you messed up
Did you Wipe cache and davlic cache after flashing?
Otherwise Just reflash again and do cache wipe and see if it would work for you..
Next time always do a system backup in settings and transfer that to PC so you can restore it..
See in you situation I would uninstall WhatsApp and restore it from backup so I wouldn't have to reactivate WhatsApp and no loss of chat history.. etc
Otherwise you would have to reinstall all the apps..