With the DTAs not working it could be the signal strength. Comcast can check the signal coming into the house. Any outside work is no charge.
Do the DTAs show a message on the television something about signal interruption? If so that indicates a signal problem coming in. Double check that all connections are tight. And if possible run the main cable input into one splitter and run all the television feeds directly into each box from that one splitter. The more splitters in the mix the more the signal strength goes down. Also make sure that the cable is RG6; works better with the new digital signals. And the splitters should be able to pass 1Mhz signal; should be written right on any splitters. If there are old splitters they can be replaced with new ones and Comcast carries those.
I have 3 DTAs installed and working fine but the Digital Cable Box has green screen saying Guardian has detected need to upgrade software and will take 20 min or more. After 12 hours and still no change, I turned off and back on. Then used the Comcast chat help. They did somethey they said fixed it. This was after hours of fooling with it. Still get green screen saying upgrading software. I have moved TVs. All TVs worked fine with straight cable. Internet works fine. Anyone have similar issue and found a fix?