Nighthawk M1 battery charging problem

I received a Netgear Nighthawk M1 23 May 2017 as a replacement for one I received in March. The problem is similar and happened almost two months to the date –

• The Netgear has been working well, but last night it wouldn't recharge, and now it seems totally dead.
• It had recharged [via wall mount socket] to approx. 80%, and yet when I returned around 10 mins later the charge had totally drained so that there was only one bar in the battery image.
• I tried recharging instead via the USB port in my computer, and went to m.home, but while I still had wifi, for a brief tine, the page just kept trying to load. I checked a Netgear support page, and other people had had the same problem, with the battery draining rather than charging. They thought it was the adaptor.
• Now the Netgear won’t turn on, no lights, nothing. No lightning bolt to show charging. 
• I have removed the battery and put it back in, and tried to reboot the router to no avail.

Is this common with Netgear Nighthawks? Should I buy a nbew battery? Is it the adaptor? Desperate minds want to know!