3rd class transfer not working

Hi folks. I have been trying to do the 3rd class transfer with my lvl 76 Prophet sub. It says I can be a Hierophant, and when I click on the give me the transfer, it offers a soul crystal. I pick one and it says I have to come back as original class. I haven't had this problem with the other 2 subs I did this with. Any ideas? Thanks.