This is also happening to me.  I can't update my jetpack.  I can't do it via the screen on the device or the admin.  There is a file upload feature for new firmware but I don't have the firmware available.  I have logged a trouble ticket with Verizon but they responded that it was "poor signal".  Clearly I need to find the real technical support folks.

here's the info from the admin page:

Manufacturer:Netgear, Incorporated

Model:AC791L

Firmware version:NTG9X35C_02.08.29.00

Firmware build date:2015/08/08

Hardware version:2.0

I have tried the reset.  that does nothing.