Do you have the GOTY edition by any chance?
The standard edition of this game is no longer available for purchase from the Epic Games store.
It has been replaced by the GOTY edition, with players owning the standard edition being offered to upgrade to the GOTY edition for a price.
We’ll need to do some tests on our end to see how, if at all, this affects the trainer. Please bear with us. 
UPDATE - GOTY Edition.
We’ve done our tests.
If you have World War Z GOTY edition, then a separate trainer will need to be made for this game version, since the game’s developer has not kept the game engine’s code between the two versions consistent.
We have added the option to vote for it in the WeMod desktop app.
