Comodo Firewall blocked VAC.

Hey guys, recently I wrote in “Steam Support” with a problem: “An issue with your computer is blocking the VAC system”. You cannot play on secure servers." They responded me that I deleted your product because it has problems from Steam. But I don’t want to delete your product.
Maybe there are solutions to this problem ?
Sorry to my english.

Check the event logs to see what was being blocked. I play steam & VAC protected games without issue.