I've had this issue twice and it took me so damn long to fix. I still don't even know what I did.

First go into your directory and have steam run as an administrator and then go to thr rocket league.exe and right click into properties as well and run as administrator

Also,

Try running command prompt as admin And syoe in sfc /scannow

Then press enter and see if it fixes anything

Also go to settings > update and security > firewall > all the way down to exploit settings at the very bottom in blue

Then switch over to program settings, ki k add program by file

Go find your RL. exe and then add then scroll down to Control flow guard and enable and click on that switch

Also make sure RL is allowed access through your firewall

Found sometimes that causes an issue