This set box does not match the account setting

As said in the subject, the main DVR box (model number: ISB7500 / last 4 GUID: 1096 ) is having issues connecting to the router (not 100% sure that is the issue though). After unplugging and restarting it, it loads with the gear and loading screen. Then, loses signal and goes back to the same screen. It then goes to a blank screen with a red X and a blue number 3  underneath. We have already fixed the other 4 boxes throughout the house, but the main Receiver box is still not re-syncing/connecting. We have already been on the phone with customer tech help as well. They could not fix the issues because they said the box was not connected to a yellow Ethernet port (connected to the RCA cable port) and was never connected through the Ethernet slot. The only ones that are, are the two wireless boxes ran through the wireless receiver attachment. The last two receiver boxes are ran through the same RCA cable as the DVR box. They are working (They are the new boxes ATT sent about a month ago). The new boxes they sent to replace the wireless and DVR would not sync up, so we sent them back, and left the old ones in.