During the match, game files were corrupt and needed to verify the files. doing so the game is unable to verify or download content, it is needed to re-download the game.
I'm getting this as well. Got briefly banned because the game complained about corrupted files right after joining a match. Integrity check was refusing to run and I had to reboot my PC to make it work.
Same here with the same file "pak01.vpk". Right after a few seconds on the Rail, M-ID: 20289532, also resulted in a timed ban from Matchmaking...
Verification didn't work even after several steam restarts.
Managed to start the verification process after updating CS2.