Replacing a switch where power comes thru the fan to the timer switch, with only 2-wires?
You got the wrong timer switch.  You grabbed one of these digital jobs because you're too cool for school.  Unfortunately your wiring is not. 

What you need is the trusty dusty mechanical model, available in any "max time" you like.  That one's an hour, you can get 15, 30, 2 hours, all the way up to 12.