Nighthawk R7000 AC1900 Smart WiFi Router Prevents Internet Access

After four days back and forth with the Internet company's tech support, they kept swearing the router went bad. I went out and bought a new one, and same thing happened. They said they'd have to call a tech to come to the home as they were sure their modem wasn't the problem since I could get online directly with the modem to computer. On a whim, I went out and bought a new modem, plugged it into the router, and the ethernet plug worked beautifully. So turns out something was going on with their router where it wouldn't go from modem to router to computer. When I tried this way, with the old modem, both the new and old router wouldn't acknowledge the cable to from the modem to the router, no matter what cable we used. But the new modem worked with both old and new router... took the old modem back to the company and was told there was possibly a short in the modem, otherwise they can't explain why the problem was happening.