"stereo*2 isn't a standard name for a surround mode so we can't say what it is supposed to do.
In standard stereo mode in a surround system you would hear the left and right front speakers and maybe the subwoofer. I can't think of a stereo mode that would only have the center and sub. A surround mode with a mono input might do that.
Go through the system set up and make sure all the speakers are working and the levels set correctly. Then follow jsmithepas' instructions above to find a mode that plays all the speakers. The owners manual usually has an explanation of what each surround mode does and with what input type.