[Steam] Cant join Portal servers

When I click to join a portal server, I get the map loading screen, I hear in-game sounds of gun fire, grenades, and vehicles; but before the loading bar finishes, the sound cuts, I get a black screen with the BF6 emblem in the middle of the screen, and I subsequently get kicked back to the Main Menu screen.

I would offer a video of proof, but this website doesn't support it.