Hello Damian Partlow
We don't recommend disabling Device Guard unless you understand the risks involved.
You could try following steps:
Open Windows Security, go to "Virus & Threat Protection," and enable "Controlled Folder Access." Then, add the game's executable file (usually ending in ".exe") to the allowed apps list under "Allow an app through Controlled folder access."
Then check if the game has added into whitelist.
Regards,
Karlie