Have your players got banned by
CS:GO Anti-Cheat: Cheating ConVars Plug-in?
If not, maybe it's because you used
smac_cvars Plug-in which is pretty outdated and seriously not optimized for CS:GO.
Anyways, you can install version 2.0 of
CS:GO Anti-Cheat: Cheating ConVars because I have upgraded the Plug-in and it's working like a charm.