TRM250 uses modem which supports following mobile standards:
Even though LTE Cat M1 is a part of LTE family of technologies, it is not the conventional LTE solution used for daily consumer needs. It is oriented to low power consumption, low data rate devices and applications usually related to IoT field. Due to that it might simply be incompatible with your carrier or data plan.
Does your carrier supply LTE Cat M connectivity?
Does your region have LTE Cat M1 coverage?
Does your SIM card support LTE Cat M1?