I have nothing in my inventory last I checked. And I just checked again, there is no box. I originally logged into an alt, but I did NOT claim it on that character, instead I went to my main (Which is only 145CR) and selected there. Then I logged out and logged back in, but there is nothing new in my inventory.
did you choose to advance the character on the character select screen? accepting the gift does not grant it to that character. it gives it to your account.