Z3 can't connect 4g

[Rz8]

My device xperia z3
It doesn't connect 3g and 4g network but working on 2g network.Sometimes connect on 3g with poor signal for few moments, then lost the signal and go emergency mode. I try all network preferable mode but don't work. my sim is a 4g and it works other mobile all network mode. How could I solve this problem?

[Uliwooly]

@Rz8

how old is the SIM card? do you have the correct APN settings? 

[Rz8]

My sim card is new 4g sim. And correct apn setting. I use gsm only. Other mode doesn't work. Sometimes 2g network updown and go to emergency mode and 2g network not so strong. Have it hardware problem or software? My friend says it anteena or motherboard problem. How can i slove this problem?plz help me.

[Uliwooly]

@Rz8

If you have it set to GSM only, of course neither 3G nor 4G will work 

Settings > More > mobile networks > preferred network type > LTE 

[Rz8]

I try this mode that you mentioned.

When i registered on 3g or 4g shows can't registere on this network. Then i select 2g , it registered on this network.

[Uliwooly]

@Rz8

if you want to use 3G or 4G selecting 2G will NOT work

[peasplease]

It's not the SIM. It's not the network. I've had SIM cards from ATT&T and TMobile with the exact same problem. No signal.

BOTH SIMS work perfectly in my old XA in all the same areas and places I go. 

What's the solution? Why is it so hard to get this sorted? I don't mind sending it for repair but everyone I have spoken to wants me to solve in Xperia companion or go to my service provider, etc. It doesn't work. The phone is now wiped clean. What next?