Enabling LTE

[Marc Murphy <marcmltd marcm co uk>]

Hi All
Been trying to get this to work for a while with no success and wondering if it needs to be unlocked somehow.

Background is I'm using Three(3) as the provider in the UK.  SIM is enabled and if placed in a mobile phone 
supporting LTE (4G) it will connect and register on the network no problem.

In the embedded system I am using I use the same SIM with a variety of modems/modules to attempt to connect 
to LTE.  All modules have capability and support the 800MHz band for Three's LTE service.  When enabling the 
modem with mmcli it permanently states searching and not registered.  I have tried with single and dual 
antennas with no luck.  

The dual antenna I am using supports frequency range: 
791~821MHz
832~862MHz
1710~1785MHz
1805~1880MHz
2500~2570MHz
2620~2690MHz

Looking on the iPhone diagnostics screen when registered to 4G it is using the band 832 - 862MHz, so surely 
the mPCIe modems should connect.

If I swap to a 3G antenna on mPCIe modems it will connect first time on 3G.

My main query is that why can an iPhone connect and us the 4G signal and the multiple modems not ?
ZTE ME3630 E1C mPCIe 
SIMCom SIM7500SA LTE mPCIe 
SIMCom SIM7600E-H LTE CAT-4 mPCIe EU
Telit LE910-PCI (LE910C1-EU)

Do I need to unlock the feature on the SIM with a pin ?

Any help appreciated to maintain the rest of my hair!

Thanks
Marc