Internet goes down when cablecard and tuning adapter are connected

I have been running HDHomerun Prime with a Cox cable card and Cox Tuning Adapter successfully for years. Suddenly my internet and phone went out. After hours of trouble shooting I swapped the Cox Panaromic modem, cable splitter, and all coax and ethernet cables out and still no internet. I found if I remove the HomeRun and Tuning Adapter from the system my internet and phone work. I then swapped the tuning adapter with the same issue.  At Cox request, I put in a new Vecima tuning adapter a month ago and all worked well. I have made no other changes to my system other than Cox downgraded the speed of my internet just before the problem started. Could Cox have made another change that causes this? I am at a loss on how to determine if it is the Cox Tuning Adapter, Cox Cable Card, or my Prime. Any suggestion are welcomed. Thanks.