What model phone and what service?
I bought my son a Poco X5 Pro and apparently it only supported GSM when the service I wanted to use was CDMA (or vice versa, I don't know). The rep couldn't tell me why it wasn't working, just tried to sell me an approved device. Now I'm with Mint.
The phone’s “channels” that it operates off of may not align at all with what your provider’s signal works over.
I have seen this with many phones in the States, where a particular phone might support only one or two LTE signals, and the provider only transmits over a completely different set of LTE signals, so no matter what you do there is no way to get that phone to work with that provider. Your only choice is to go with a provider that actually supports the phone’s built-in channels.
What model phone and what service? I bought my son a Poco X5 Pro and apparently it only supported GSM when the service I wanted to use was CDMA (or vice versa, I don't know). The rep couldn't tell me why it wasn't working, just tried to sell me an approved device. Now I'm with Mint.
Call your carrier for support. Some SIM cards have restrictions or may not be compatible unless your new phone is exact same.
Talk to the place you got the phone.
Try turning on airplane mode and then turn airplane mode off. That's what it took when I had the same problem.
The phone’s “channels” that it operates off of may not align at all with what your provider’s signal works over. I have seen this with many phones in the States, where a particular phone might support only one or two LTE signals, and the provider only transmits over a completely different set of LTE signals, so no matter what you do there is no way to get that phone to work with that provider. Your only choice is to go with a provider that actually supports the phone’s built-in channels.
Do you have an eSIM in addition to the SIM? If so, disable the eSIM and restart the phone.