How to ascend to abyssal lich. I got the invitation, beat the boss, now what?

I have the option to ascend. I have all my ascendency points. I beat all rounds of boss. Once the dragon vessel is beat at last stage, an npc comes and you talk to that to ascend.

I somehow got it to work. The only conclusion is that the first attempts were somehow bugged out and the option to select the liches or the finger was simply not present at all even after defeating the boss. If anyone else has had this issue maybe we could compile some circumstances for a potential bug report