I saw someone else had the same problem and it was not solved (2 months ago). Maybe someone has an answer now?
I installed the plugin and copy paste the experiment code. So far so good. But when I save it, it and I go back and check if its there - it has dissappeard. I go back to google experiment, and it says (of course) that the code is not found.
Appreciate if someone found a solution to this issues.