Hey guys, replying here because I just managed to solve the same problem I had.
First, please ensure that there are indeed no characters transferred on the account (even though on the website it says that there aren't, you should log in and check).
If it is the case, then you should register a new account, get a new token and try transferring them again.
I just did this and it worked, so it seems sometimes the characters don't get transferred. Good luck!