Translation:Are you going to travel to Mexico tomorrow?
"Are you going to Mexico tomorrow" rejected, reported. In English the "travel to" is mostly redundant/implied
I believe it's because you have "viajar" in the sentence so you should be translating it with the verb "to travel". I wrote "Are you traveling to Mexico tomorow" and it was accepted. "going to travel" was not necessary.
Are you going to Mexico tomorrow? should be accepted. Just my humble opinion. I don't know any English speaker who would say Are you traveling to Mexico tomorrow? That sounds so unnatural.
Why not use "go" instead of travel? And it was rejected "Are you going to go to Mexico tomorrow?"
"do you travel to mexico tomorrow" was rejected, and means the same thing in English except more concise. Sometimes Duo takes literal translations and sometimes it takes the implied meanings that only it wants.