Nighthawk R6700v3 restarting & unable to access Netgear setup

[schoolboy1503]

I am running a Nighthawk R6700v3 router.  The last two weeks it has been powercycling itself sometimes every 5 minutes.  I am running ExpressVPN with it and am now unable to access the Netgear portal, even with a full reset of the unit.  Unit will not accept the default admin/password combination when connected via cable and keeps bringing me back to the router login page.  

[plemans]

Expressvpn is its own 3rd party firmware. You'd have to go through expressvpn for help.