Netgear NighthawkM6 from AT&T DOA

Trying to setup Wi-Fi in our new home in rural Upper Peninsula of Michigan, seems like AT&T's home cellular Wi-Fi program might be good as we've been with AT&T cellular for years. We had prior experience with cellular Wi-Fi from AT&T prior to moving to Michigan even though we thought the service was spotty @best.
The AT&T tech was having issues with the touch-screen response (when it would respond) but seemed to think the unit was ok; he sent me home with it after getting the financials all set.
At home, put battery in like @ the store and nothing for several tries; I called the store; tech said sometimes this router has issues with the battery not seating well in the cradle; tried several times to make a connection; nothing.

Watched a youtube video from Netgear on the AT&T router and the video said you could increase the range of the router to 2,000 sq ft if you take the battery OUT and use the AC converter plug; OK! Unit powered on but little else; would not boot the home menu; would restart at random, I tried resetting by every means I knew (and I've been dealing with PCs for 40 some years) with no luck. Finally got to a screen saying 'Connecting . . .' and waited over an hour . . .

Called the store, gave them my story, the tech checked with his district manager and told me to bring it into the store (45 miles away) and they would issue a return for defective equipment. Would I get a new one immediately? You guessed it . . . No, I have to wait for a new one to be sent to me from the return center. What do you want to bet I have to wait on the defective unit to GET TO the return center, then someone to look it over, and then get a new one sent to me? They better not send this one back!