If you are at -40 with both then reputation shouldn't be the issue. And the Conjurer in the icemist Fjord is indeed the correct one.
Did you kill any of the knights standing next to the Conjurer?
Since if you have the gold and the orb, the dialog option should appear? Can you show me some screenshots of the dialog options that are available?
I think it's the user called chiller Rex on discord, if so, I have his save file and it seems like a glitch
Here the backup
I didn't had time to look on it deeper, but at least the dialogue is not an option for him.
I recommended to use older save (Was only lvl 11,so nothing big) and redo everything.
Ps: not sure if it's the same user, but since it was few hours ago, I think it's the same one