I believe that there is some button on the garage door unit that you have to press before linking the garage door opener to the home link buttons. (do this if below does not work)

Have you correctly attempted to link the garage door opener to the home link?

With the engine on, Press buttons 1 and 3 until the LED flashes rapidly.
Then hold button 1,2 or 3 while pressing the button on the garage door opener until the same LED flashes rapidly.

I hope this helps.

Regards,

Arthur