Goodman GMNT100-4 Unit- Blower Motor Works for Air But Not the Heat
Check to see if the HEAT terminal on the circuit board is getting energized when the blower motor should be running.  If the motor is getting power, but not spinning, then there's a problem with the motor. If the motor is not getting power, then there's a problem with the circuit board. 

If the motor is getting power, but not spinning, it could be:


A bad connection between the circuit board and the motor
The wrong motor lead landed on the HEAT terminal (but that would likely just spin the motor at the wrong speed)
A bad motor capacitor (Probably not if A/C works)
A bad motor winding


If the board is not energizing the motor terminal, it could be:


A bad timer
A bad relay
A bad circuit board trace