hmm none of mine are working and I linked them days ago.
It corresponded to the number of emails I got (I use the same email address). I received 5 emails, was able to login 5 accounts. Not all of my accounts linked to my active account can be logged in for RTB yet though.
My guess is that it's batch processing - doing X amount of emails after activating X amount of accounts, etc. and that it just hasn't gotten through all of them.
I didn't login before to see what the accounts said. It's possible that when I logged in, that set the Description to Return to Britannia promotion, because my other accounts are either paid or closed or not linked. My closed accounts will not work yet. The majority of accounts which did not work for me are not linked, but if yours are linked, then I don't know other than it just hasn't gotten to you.
And there is nothing in the status area either - just lists all of the expansions on the account.
Good news - it's good through October 5, which means we'll get the Halloween gifts in addition to the 15th Anniversary gifts on the RTB accounts if you are into that kind of thing. I have enough pumpkins to last a lifetime, but I know there are people that collect them and a lot of other stuff.