Bad SIM, Modem or Router? LB2120 4G LTE Modem & Nighthawk 1900 Router

I live in a rural area and use the LB2120 modem, a SIM card with a Verizon APN and the Nighthawk 1900 router. This has worked great for the past year.  We had some power outages and noticed a loss of our connection, but after unplugging both and re-starting them, I was connected again.  I did purchase a UPS and power outages are no longer an issue.  All was fine until two weeks ago,  I lost our internet connection and noticed the modem's power LED was blinking green.  I could not find a solution anywhere online.  I brought the modem to work and had my IT guy test it, he reset it and once he did, the power LED is no longer blinking green, but is a solid amber.  All the lights on the router that are regularly lit have been lit the whole time while this has been going on.  I bought a new modem, same exact one, and just opened it last night and as soon as I plugged it in and powered it on, the amber light is solid.  Could it be a bad SIM card?  Could it be my router?  How can I tell?  Please help, I am not computer-savvy and I am frustrated not knowing how to solve this.  Thank you in advance!