Xperia Z C6603 problem 4G

Hi all members please I need some help with my Xperia Z c6603 when I research I find the 4G network and I install an app to turn only 4G but there's no signal 📶 4G :confused: please help me :'(

from xda-developers http://ift.tt/20uTsHR
via IFTTT