There is a difference between American and English spelling of this word.
I'm not sure how to report this, but what Duolingo is offering as the correct translation really isn't English: "Where is your trip going?" My trip is going nowhere. My trip is not a thing or being that can move. Perhaps one could ask, quite colloquially, "Where is your trip to?"
When you get marked incorrect for a question by Duolingo and you disagree with their decision, there is an option to report it. You can leave comments here or simply check the box "my answer should have been accepted". It's on the bottom left if using a browser; I can't remember where for apps, but I know it is available as I've used it many times (and had some of my suggestions accepted)!
On a previous translation example, the German phrase was "wohin geht die Reise" - correct answer was "where is this trip TO" So, "TO" was OK then. Now with "Wohin geht deine Reise" the offered translation does not mention "trip" nor "to"? With Wohin I get that it's accusative, because you are going somewhere, but I would have thought for consistency, we could use "trip" and "to" ?