4G Modem Disappeared? - GLx750

Has anyone else had the 4G modem randomly disappear from their router settings menu? See below. The 4G modem portion, normally at the top, is completely gone. Have tried updating firmware, flashing original firmware, no luck. Has occurred on three of our GL x750’s.

Are the external antennas always connected?
Which firmware version is operational?

Can you ssh to the router and use logread to get the log?

Maybe modem died or usb interface died.

Currently using 3.211, and yes the external antennas are connected.

Is there a way to check if the modem died? I’m not familiar with SSH, could you explain on how to check it?

ssh is easy. Pls refer to SSH to the Router - GL.iNet Docs

If you install luci (advanced settings) you can get the log in luci as well.