Turning off windows firewall worked for activating on all 3 but SSZ crashes upon loading the actual environment after the cinematic with the trainer active, I tried waiting to activate till after but then the cheats didn't work and it crashed after the next stage cinematic. Could be some new update was released with at the time of the sale.
Have you tried 6. STRIKE SUIT ZERO TRAINER (PATCH 10.28.2013)?
That was it, though I did notice that the plot trigger doesn't activate in DS3 now with the trainer active, I'll post when I look into it more though :/
I played it co-op with another CH member not too awfully long ago and the trainer worked fine for both of us the whole game. I'm pretty sure there hasn't been any recent updates. Seems like we might have had to reload between chapters or somewhere though.
[Edited by element5, 3/14/2015 7:51:32 AM]