I went through a similar set of steps for everyone else, but wanted to post the differences in case it helps someone with the same issues, because my car had some quirks in how it allows you to set up the HomeLink buttons.
My car is a 2017 A4 Allroad (B9), and I have a WDHA-12R, but I’m sure the same steps would apply to any A4 B9 with the Wayne Dalton gateway. The car doesn’t let you at the HomeLink buttons willy-nilly; you have to request permission through the MMI to program them (or press the button and then accept the MMI prompt to program it). This means that the instructions don’t work well for the steps that involve holding down the buttons on the car transmitter, because the car keeps stepping in to ‘help’.
First the easy part, I paired the gateway with Vera (running UI5), and created the scenes, all per the instructions in ChrisTheC’s excellent post here.
Then, I had to pair the gateway with the car. To do this take the gateway out to the car (no AC power needed - it contains a battery which I was assuming is good):
[ol][li]Press button one on the car transmitter, and say yes to the prompt to program it.[/li]
[li]Hold down button one on the gateway until the car transmitter light flashes green several times, Bizarrely the hazard lgihts on the car flash too. [/li]
[li]Accept the prompt to synchronize the button, follow the instructions and hit “yes” when asked if the garage door is moving.[/li][/ol]
Next, you have to sync each button on the gateway with each button on the car:
[ol][li]Hold down the button to sync on the gateway; the light will come on, then go off in a second or two[/li]
[li]Release the gateway button as soon as the light goes off[/li]
[li]Press the button on the car transmitter; the light on the gateway should flash to confirm[/li][/ol]
…and that’s it. I didn’t have to do anything special with holding the gateway on a weird angle, it seemed to have no problem sending or receiving at any point.
The programming menu in the MMI indicates two different modes for the buttons; ‘UR’ and ‘D’. I left this on the default of ‘UR’ and it seemed to work just fine.