I'm not convinced, I bought a factory refurbished 2555lmt last week from tigerdirect and it only came with a normal TA20 charge cable (unit says LMT on it), traffic has not worked at all for 3 days. Today I swapped the cable for the traffic receiver type GTM 25 from an older garmin of mine and all of a sudden the traffic on the unit started working again. I'm about to send it back to tiger as the cable is $70+ on its own.
I had same problem as yours.(Bought it from TigerDirect too) I called Garmin, they guided me to fix the problem. Unfortunately not receiving traffic update still. Sent back to Garmin and replaced. Will keep you posted once I got replaced unit. According to Garmin, if you use GTM 25 it should work too.