Guild Wars 2

Any ideas why I cannot get hit points while trebbing from Garri Trebspot to Bay?
Bay corner where splash damage affects wall.

3 Guildies using Treb from Garri Treb spot high upon cliff.
They get hit points, one guildy has no points in Treb mastery.

I take over Treb and using skill 2 let the bar fill and release itself.
I do not move aim. I get no hits displayed and even guildies check wall as projectile hits, no damage.

Guildies take back over and get hits again.

I have 5 points in treb line (plus damage).

angry bird is angry