If it happens also when you alt tab
Then you need to after you launch the game alt tab then click on the game then click on the black screen that shows until the game appears do this until it works
If this doesn't work idk man you might to fix your game files

OGagentorange if it doesn't work also see this one it got the one from Conzt_Waltz
And the one I found it works https://forum.plutonium.pw/topic/37249/how-to-join-friends-if-you-can-t-enable-pnp-or-do-the-
port-works-for-t6-also

Conzt_Waltz it didnt work but i found another way and its so easy
just dowload radmin vpn (hamachi didnt work for sum reason)
and copy the ip address and open the console and type connect "ip address"of the radmin vpn address and it worked with and without mods and in every mode worked and whats even better it worked for bo2 and a lot of games but thank you for responding to me, everyone thought my qusetion was dumb

zskbp "unlockall" and unlock everything

im on pc

Verify the files in Steam.

what the spruce

Report them to the owners of the server you are playing on.
Decent server owners will let you know while playing on their servers. Usually its !report or through their Discord server.

Go to your steam library, then go to the game in your library but don't start it. Click on the options and select the game properties (I forgot what it's called) and look around the properties. There should be an option called "Verify integrity of game files" or something.

ty JezuzLizard this worked for me 🙂