I understand and I addressed that in my reply. If you read my entire reply I also said “If you have two then perhaps name it simply “John Garage”. As in “Alexa Open John Garage”.”
I tried to address your problem. Sorry if you don’t like my suggested solution.
I find with Alexa you need to get a little more creative. Perhaps call the doors by the car names usually parked there. Try different names until one works.
I have a light on my main floor which I originally called “Main Floor Light”, every time I asked alexa to “Turn on Main Floor Light” it would respond with “Which light did you mean?”, and I would have to say “Main Floor Light” again and it would work. It drove me crazy. So I changed the light name to “Living Room Light” and it works perfect now. In fact if I just say “Turn on Living Room” that seems to be enough.
By having unique words in each name that word becomes the key to controlling the item.
Perhaps try these names
"Left Garage, Right Garage"
“Acura Door”, “Lexus Door”
“Red Door”, “Green Door” (based on car color)
“Car Door”, “Truck Door”
You get the idea. If you insist on the issue of making “Jon’s Garage Door” work then I suggest you contact Amazon Echo Support.
BTW: have you used the Echo Voice Training so it knows your voice, accent etc ?
Does Alexa say “OK” when you say “Alexa, Close Jon’s Door ?” if not then the issue is Alexa not understanding. Even if it does say “OK” I find many times when I say turn “On/Off” or “Open/Close” alexa gets it wrong and issues the opposite command. So watch the ide live log and see what command is issued when you make the command. Also try being real clear on words open and close as in “Alexa, CLOSE…Jons Garage Door”