The TF expression pedal will autocalibrate at power-up and when the pedal is removed and re-inserted, so the last suggestion is good.
But, if you have to do this all the time you will become annoyed. Probably, first thing to try is another pedal, preferably one with a record of sucess with TF. See FAQ for details.
Some pedals will not work well – particularly those with a very high resistance pot. Also, look for an adjustment knob on the pedal.
