Hey,
on my Server you can use sv_cheats convars like ttt_force_traitor but i did not enable sv_cheats, it is 0.
Please help maybe it is a bug.
Greetings
Update your TTT.
I got the latest version.
You are playing Trouble in Terrorist Town, version 2017-04-20.
[editline]13th August 2017[/editline]
I solved it now myself it was because i had a ancient version of Spectator Deathmatch installed.
After an update it works now!