I had the same problem with my Rebel T3i and found by Canon support the real solution.
There is a movie mode menu on the T31 that you need to get to. To do this, first set the camera to movie mode, THEN press the menu button. When you do this, a movie menu appears and one of the items is "Remote". It is either activated or deactivated. All you have to do is select "Activate" and the problem is solved.
More generally, it appears that the cameras come standard with the remote control disabled. You just have to go to the movie menu and turn it back on and you're ready to go.
I'm not sure what the details will look like to get there with your camera model, but I think the process will in all likelihood be the same.