MR1100 suddenly cannot connect to cell service

Help! MR1100 Suddenly Stopped Working – 'Mobile Broadband Disconnected'"

Hi all – hoping someone can help!

I have a Netgear Nighthawk MR1100 (out of warranty), which worked fine for about a year. But suddenly, as of yesterday, it stopped connecting.

Error message on boot-up:

"Mobile Broadband Disconnected – Your data connection is disconnected."

My Setup:

• Carrier: Consumer Cellular (an AT&T network reseller)
• Location: US suburban metro area with decent AT&T coverage (usually 3 bars)

Here's What I've Tried (No Success Yet):

• New SIM Card:
  Consumer Cellular sent me a replacement SIM and updated their system. Inserted the new SIM — still the same error.
• Reset & Reboot:
  Used the reset button inside the MR1100. Also performed a full factory reset via the attwifimanager page. Rebooted after each change. No improvement.

Other Notes:

• Voice service works fine in this area, but mobile data is typically average — usually 3 bars.
• After all attempts, the same error persists.

If anyone has suggestions or ideas, I’d greatly appreciate it!

Thanks!
— Navibean9