thomson 28wt25us combination tv/dvd?

A friend recently joined SKY and the fitter fitted the power line of the sky box to the same plug as fitted to the TV/DVD--since when the DVD player does not appear to accept that any disk is in the machine which it clearly has been taken in via the draw mechanism. I am of the opinion that the fitter was wrong and that the power supply for each article should be on its own plug.Would this be the cause of the problem re the player showing no disc on the tv screen