When I first got this skill, I used to get an echo about failing to pin my target. I don't get this echo any more. As far as I can tell, I am not long even attempting to pin after I bash someone whilst wielding a polearm, and I tried a couple of trips too without any attempt at a pin being noticeable.

I can get both the "working" echo:

You trip an ugruk hunter and he goes down!
Your trip scratches an ugruk hunter.
Seizing your chance, you stick an ugruk hunter with a long titanium polearm as he hits the ground!
Your pinning blow decimates an ugruk hunter!

... and the "not working" echo:

You race up to an ugruk hunter and kick his legs out from under him!
Your trip grazes an ugruk hunter.
You fail to bring a long titanium polearm around in time to pin an ugruk hunter down.

You won't get an echo if you have no chance of making a successful Pin in a given situation, however, and there exist circumstances which are by design and can cause this.

valguarnera@carrionfields.com