I have shibby's latest build (97 I think) on an RT-N66U with a Novatel U679 LTE stick.
While it took a bit of work getting the usb_modeswitch right, I did manage to eventually get the WAN i/f up and all was perfect.
A couple days later, a power outage cycled the power on my perfect Tomoato router - and now the connect script is failing every time.
I've manually issued usb_modeswitch - the modem is DEFINITELY in the right mode.
I've restored a backup config taken immediately after I got the modem working the first time - thinking that perhaps I'd made some changes that I'd simply forgotten about.
It's been a VERY long time since I've used pppd and "AT" commands - I simply don't have the chops to get to the bottom of this.
Perhaps someone can give me a quick 3G modem diagnostic guide?