Mae Trin Challenge completed with no reward
I think the reason was I probably joined a team that had already wiped? There was only one individual present when I joined but they had already cleared the first mob. In any case, I finished later, but thought I’d leave the post up in case there was an issue.
There should be a marker if you’re eligible to complete the challenge and it counts down the time. Did you have that?
The challenge timer doesn’t start until you enter the arena. When a group completely wipes, it will end up out in the hall — there’s no visible difference between a group that hasn’t entered the arena yet and one that wiped.
So I think your theory is probably correct: the initial 5 wiped, some left, you replaced one of them, and the timer had already expired before you had a chance to get in.
For what it’s worth: any group that can defeat Mai Trin is going to finish within the time limit; it’s fairly unusual to have a group that can survive for more than 25 minutes without being able to do enough damage to make the fight quicker than that.
Played Guild Wars, and have had GW2 for 4 years now