Now i can't start plasma kde

i used to use this command to open up display so i can access a desktop version of debian 12 bullseye.

Xephyr :2 -resizeable -fullscreen &

sudo -g root DISPLAY=:2 startplasma-x11

But now it won't work, i get several errors.
worked yesterday but today i was able to upgrade some debian security options, I can show the code if needed,

but now these are the errors I get.
I opened plasma this way because the other ways had never worked, it used to return an error and do nothing for me, tho I don't currently remember what the other commands were or what other errors it gave back to me.
What can I do? pretty new to Linux, had debian 12 bullseye installed a while back

Xephyr :2 -resizeable -fullscreen &

sudo -g root DISPLAY=:2 startplasma-x11

[1] 2877

(EE)

Fatal server error:

(EE) Could not create server lock file: /tmp/.X2-lock

(EE)

QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-MyUserName'

$DISPLAY is not set or cannot connect to the X server.

[1]+ Exit 1 Xephyr :2 -resizeable -fullscreen