CarnaIt says something went wrong, but I am already in
Joining a school only happens once. A second attempt reports a clash — which means it worked.
If you enter a code and get an error saying there is a clash or that this has already happened, the most likely reading is the good one: you are already in, and the page you are looking at is out of date.
Joining a school is deliberately a one-time thing. Once your account is linked, a second attempt cannot succeed — so the error is the system refusing to do something that is already done.
What to do #
Leave the page rather than trying again. Close it and open Carna fresh. You should land inside your class.
Retrying the code will give you the same message every time, because nothing is wrong to fix.
If you are still outside after reloading #
Then it is a different problem. Work through My class code is not accepted, and if none of that fits, write to us and say what the screen said word for word — the exact wording tells us which of four things happened.