GL-X3000 "No Modem device found"

Technical Support for Routers
1

My X3000 has been stable for ~1 year. But a few weeks after upgrading to 0411release1 the modem appears to have gone offline. On the Admin Panel home page I see a red warning "Unknown error occurred. Please check the network environment or reboot the device."
Rebooting does not help. Power cycling does not help. I'd like to avoid a factory reset if possible (it's a LONG way away!!).
Any suggestions?

2

I'd be using the latest update 4.4.12 or even 4.4.13. Also, what version of module firmware are you using. I'd guess that it is an old version and you need to update that too to a more stable version.
Run this AT command are report back - AT+QGMR

3

The modem isn't visible in the Admin Panel, but I can interact with it using socat:

/usr/bin# socat - /dev/mhi_DUN,crnl

AT+QGMR
AT+QGMR
RM520NGLAAR01A07M4G_01.201.01.201

OK
4

http://download.gl-inet.com/download/RM520GL-modem_firmware

Download and install RM520NGLAAR03A04M4G_01.202.01.202.zip
Module can easily be updated using latest firmware so I recommend doing that first. My router has been rock solid with the latest beta firmware(4.4.13) and the above mentioned module firmware but it may also depend on your SIM carrier.