%1 is not a valid win32 application error

[Wantaplay]

So far I have:
verified the game
reinstalled the game
reinstalled Steam
removed addons
reset the game
and nothing so far has fixed this error.

[garryplshelp]

Might be a registry issue?
Take a look -

System Help

and

https://support.microsoft.com/en-us/help/812486/event-id-7000-and-1-is-not-a-valid-win32-application-error-message-whe