@droidus no idea, did u install as pi and now running as another user?
did u install as root (using sudo), now running as pi?
see https://askubuntu.com/questions/1238389/invalid-mit-magic-cookie-1-key-message-while-running-a-program-with-the-termin
if you used my script (just copy/paste the one line from my github page) , logged on as pi, it should have done everything for you
what I do
use the OS imager tool, install the latest OS image (full desktop, code name buster) on the sd card
boot the sd card,
turn on ssh
reboot the sd card
logon via ssh from windows (or linux) machine
copy/paste my install script line into the ssh terminal window
wait…