That code used to be on my account page. Was looking for it today, not long ago, to no avail.
Then I Googled how to find it and yep, it was part of that loot box. Lots of explanation and a blue bar "share your referral link." Tested it to my 2nd email and it works.
Perhaps if the box just appeared, it may be slowly getting there.
Oh, I don't have a Tesla car either.