I created a Virtual Switch in Smartthings, then in IFTTT I created 4 applets
The first two update the switch status if the door is opened manually (outside of Smartthings)
If open garage door, then Switch on Garage Door Virtual Switch
If close garage door, then Switch off Garage Door Virtual Switch
The next two allow Smartthings to open/close the door
If Garage Door Virtual Switch switched on, then open garage
If Garage Door Virtual Switch switched off, then close_garage
Seems to work well for me