I bought The Bureau - XCOM Declassified from GOG and wemod won’t work on it, so what’s up?
I just looked over the game list, and I can see why- it is made for the steam platform, but it is mislabeled as including GOG when it doesn’t have a trainer for that platform.
Can you guys make it work for the GOG version?
Welcome! 
As stated already, the trainer is built for the Steam version of the game.
This explains why each store needs its own separate trainer: Why are there different cheats for each storefront? - #4 by Ravenfyre.
Trainers are only made at WeMod if a game on a specific platform is popular with the WeMod community. The WeMod software automatically detects how many WeModders own each game on each platform and, if it is enough, the trainer will appear in the development queue, which you can see in the WeMod software itself.
Learn more: Game Queue & Boosts - WeMod Support