No internet access Model WNDR3800

I moved to new house.  When Cable Tech tried to connect my router to modem he could not get internet access.  I allowed him to use one of thier routers (renting).  Worked for last 3 or 4 months.  Then I lost access.  After trouble shouting problem with Cable company phone support, we were unable solvew the problem.  I decided to try and use my Netgear router.  I connected it to the cable modem, I was able to see the modem on my computers and join the network fine.  But I still did not have internet acees.  So I connected an eithernet cable between the router and the computer and still no internet access.  I connected the modem deirectly to the computer without the router and got internet access.  I reconnected the router and still no access.  I rebooted the modem and reset the router to factory settings. i was able to reconnect the computers to the router network using the factory network name and password, but still no internet access.  Can anyone tell me if I might need to change the settings in the router or if there is a way I can test the router.  If not, I may have to wait until the cable company can come replace their rental router.  i would much rather use my Netgear router.

Thanks