Opens fine for me on Win 10. Link
What OS you using?
Are you running from an Admin account or run with Admin permissions?
What security software?
Is the trainer in a folder excluded from scans?
Is STEAM in OFFLINE MODE?
[Edited by CyPHeR369, 9/12/2021 2:34:01 PM]
They pushed another game patch, probably why it is now ON HOLD.