Valve has expanded CS:GO's anti-cheat tech with 'Trusted Mode', a new form of matchmaking. Valve ran a beta for the new system last month but, after its full launch earlier this week, Trusted Mode is already causing problems.
The idea is that Trusted Mode will "significantly restrict" the types of programs that can interact with CS:GO. It's now the default mode for players to launch the game into, meaning it'll block third-party programs from working alongside it. If the game detects that software, you'll be asked to restart in Trusted Mode with the offending files blocked. It's blocking cheating software, which is good, but it's also blacklisting streaming software like OBS and some graphic filters from Nvidia. There have also been some reports of performance issues, according to RPS.
You can get around Trusted Mode, but doing so is likely to take you down in Valve's estimations and place you in matchmaking queues with cheats. Overall, it would seem as though the system isn't working perfectly as intended.