Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I would say that either a sensor that tells the circuitry what position the incline is in, has failed (this is more likely if the incline is stuck in an extreme position, either maximum or minimum), or a winding in the incline motor has failed (less likely), or the motor controller board for the incline motor has failed.
Or, possibly the linkage has jammed up and cannot be moved by the motor.
Not responding to the calibration operation is typical of a hardware failure of some sort.
But tell me - is the incline stuck in either maximum or minimum position. And, if you listen carefully, is there either ticking or a steady hum or whining coming from that area of the machine, that goes away when it is unplugged?
Then it may be jammed.
Would you wish to try to fix this problem yourself, or (at this point, since it's obviously some sort of hardware or 'brokenness' issue) hire a repairer of this brand of treadmill in your area ?
OK. You'll have to unplug it, remove the outer covers, and examine the drive/linkage that raises the elevation, for any difficulty, or for dried-out lubrication leading to a seized-up status... or basically, examining it for whatever is wrong with it, outwardly, before going into less obvious details.
OK. Now do a 'live test' - after checking for either loose, or disconnected, wires or cables anywhere that you can see - and after re-seating any cables that have any dust or dirt around them.
Look for lights, status LEDs, on any board / control board, and pay attention to the indications on the console. Note LED status with the machine powered On but idle.
Then try controlling/settings on the console. Note how LED status changes, if it changes at all, when you try to set elevation or change elevation.
Let me know how it goes.