Hello Joefath1,
Welcome to the community!
Do you know the band/frequency specifications for your phone? These are the specifications from their website:
GSM:B2/B3/B5/B8 (1900/1800/850/900)
WCDMA:B1/B8 (2100/900)
FDD-LTE:B1/B3/B7/B20 (2100/1800/2600/800)
TDD-LTE:B38/B40（2600/2300）
According to those specifications that phone would have both of the compatible bands/frequencies for 2G. Strangely, those specifications do not list any compatible bands/frequencies for '3G'. With regards to LTE, that phone only has one compatible band/frequency, band 7 or 2600MHz.
While some other specification websites suggest the phone does have '3G' compatible bands/frequencies, they do not show any additional LTE bands/frequencies (see here and here). You can verify the compatible bands/frequencies here. While the phone should work on the LTE networks, coverage depends on the corresponding bands/frequencies used on your surrounding cellular towers as not all towers use all bands/frequencies. You can get an idea of your local cellular towers here.
That said, have you verified that your phone is using the proper APN? Since the device is LTE-capable, it should be using ltemobile.apn. You can verify those settings here. Have you verified the network mode has been set to GSM/UMTS(WCDMA)/LTE?
Additionally, since North America isn't likely the target market for that device, have you tried to enable data roaming? Some devices from abroad might think they are roaming even though they are using a local SIM.
Hope this helps 
Cheers
