No signal at all

Was the phone purchased in your home country or imported? If you imported it, this is a common-ish issue even today. Back when I did this with my RAZR V3i (Euro spec, same bands as the US 2G networks but didn't use the US 3G bands so it was a 2G phone in the US; but so worth it to not have to deal with MotorolaxApple iTunes). GSM carriers will accept these (generally) but these imported phones are very much at your risk; it's not on them for checking if the Euro 3G bands were not matched to the network you use.

If the phone is country native, try to see if resetting the network settings will do the trick. Sometimes it helps, sometimes not.

If neither works, it's either due to a cellular radio failure OR your carriers are crippling it because of how it identifies, which cannot be avoided because Hauawei has a unique IMEI which gives identifies the phone to the carrier. There are ways around it but it's in a legal gray area and hard to fix if you botch.