1. The TMC data comes from external sources, it is basically the same you hear in the traffic updates on the radio.
2. A solid, green dot ideed indicates that you are connected to a radio station with a TMC signal - but not that you actually receive any traffic data
3. The traffic data is not related to your map or Navcore, other than that you get the traffic info based on what map you use and where you are.
A) Try to find out what radio station in your area actually provides TMC data, add their frequency manually into the TMC settings instead of the auto search.
B) Make sure the antenna cable is as straight as possible, e.g. along the windscreen and then down but not curled up to save space - only an erected antenna has clear reception.
C) If all fail try a different MCTX.DAT (root of the TT) - the one from the 8.351 Navcore is still one of the best.