Only Simple Cable Release works/ I can't use any of the long exposure modes.

If you are finding that none of the long exposure modes on Triggertrap Mobile work, your camera could be in the wrong mode.

If you are using Press and Hold, Press and Lock, Timed Release, Star Trail, Bramping, LE HDR or LE HDR Timelapse, then your camera will need to be set to bulb mode to take the exposures. If you are using any of the other modes in the Triggertrap app, your camera will need to have a shutter speed set on a manual mode, rather than bulb mode.