Nighthawk AX6 AX5400 and existing bulk cat6a not working

[scotmicharm]

Just upgraded from Nighthawk R7000 where existing bulk cat6a cable in the home works. The new Nighthawk AX6 AX5400 is not working with this existing cat6a cable. I tried some retail cat6a cable with the AX6 and it was successful. Thoughts on how to diagnose?

[plemans]

You kind of already did the diagnosis. 

You found one set of cable run didn't work but replacing it with a new/premade did work. 

Kind of points at the cable. You can try replacing the ends on the cable to see if there's a bad pair or miswiring going on.