Saltysally1probably 1 of 2 situations you're experiencing, you may have blocked the program in windows firewall or another 3rd party firewall in which case you need to add tf2/mumble to exceptions so they are allowed to access the internet, or your antivirus see's some operations as a threat, most good antivirus software has something called gamermode which turns off the av while you play your games, just make sure to re-enable it when you exit your game.
so many commas