Does the in-wall coax go directly from the wall plate to the TV? If so, it should work. We need more information about how the cables were run, where they go and how the input and output of the DTA-50 is connected in order to troubleshoot the problem.

The best solution would be to get a Rogers HD receiver that has HDMI out. That might cost extra money but there may be offers for free rental available.

 

There should be no reason that the RF-coax doesn't work. It sounds like you have a poor or missing connection somewhere - probably related to the wall plates. If you can, remove the wall-plates and connect the coax that's in the wall directly to the TV and the DTA. Remember to tune to channel 3 and the appropriate (Cable/Ant?) input on the TV. If the coax in the wall is too short, use a coax outside the wall as a test to make sure the TV and box work (sounds like you may have already tried that).

If you've got an HDTV, you should really get an HD box.

 

His problem is that he needs to change the 1 coax wallplate with a 2 coax wallplate, one is the cable in feed, comes in from the main splitter, the second coax for the wall plate should be the coax out to the TV, here you would fish the coax thru the wall and out at the back of the tv and if u want to make it neat, put another coax wall plate behind the tv to tidy it up. and sorry the dta-50 does not come in a model with hdmi out in canada, maybe the states yes but not canada

 

That's why I asked for more info on the connections. If the DTA-50 output is being mixed with the cable signal it will not work. It could even result in service problems for Rogers and other customers. It appears that the OP has disappeared so we may never know the answer.