Must be a bug, he wont take it.
since you are not new to the game, i take it you already know if the quest might have been bugged or not.. quest bugs s**k really
try dropping charon's oar and picking it up again.. if he still won't accept it, your only way might be deleting .que files.. unless of course someone knows a better solution
if you want to try the que files, judging by this thread
https://titanquestfans.net/index.php?topic=514.msg5264#msg5264the right que file might be
c62be664ffc9b3dcc1c09fa15c9dabc3.que
i just assumed that because iirc, charon's oar quest is the one before the stygian lurker quest.. backup the que file first before you delete it
location of quest files are iirc
Documents/my games/Titan Quest/Titan Quest - Immortal Throne/SaveData/Main
if I'm not mistaken saves are still in immortal throne folder.. I'm on mobile right now so i can't confirm