ER707-M2 USB Modem -- information, please!
I just acquired a new ER707-M2 and need to setup a 4G modem connected to its USB port as a backup to my wired internet connection. There is seemingly no documentation on which modems are supported for this router, or even which mode it expects the modem to be in (Direct IP or QMI/MBIM). Its compability page (https://www.tp-link.com/en/er707-m2/compatibility/) is nothing more than a placeholder.
I have a Sierra Wireless MC7700 that works flawlessly in both Windows and Linux and both in DIP and QMI modes. When connected to the ER707-M2, the router reports "Identify successfully" but then when I enter my APN information (i.e., manual configuration via the router's standalone web interface) and click "Connect" it simply pauses, displays "Saved," and then sets the configuration mode back to "Auto." No diagnostic data is provided in the log, nor any failure message in the web interface. I seemingly have no means of determining why it is failing to connect. I can't even determine if the router is using the newer MBIM protocol to communicate with the modem or legacy AT-commands-over-serial. Any information as to how to resolve this issue would be appreciated.
