Navigator If it worked , and stoped duing firmware update , then i is a question , if it is still recognized in the system.
I belive factory defaults you already tried.
Onl way is to open a router and either connect to serial terminal and comunicate with it ( it is standard OpenWRT terminal , you can pass i.e. a command ,if modem is recognized in usb bus , you could send a command , to go to normal state via AT commands). Or you can dismantle a modem , and put it to mPCIe socket in laptop , or buy a usb-mpcie device , and do it externally.