I think aprentice is not enough. I've also done the quest between getting the main quest direction to go to Caladon and actually going there.
It should be that the only prerequisite is completing the Black Root taxes quest. Try increasing your persuasion, charisma, or both. BTW, apprentice, expert, and master have nothing to do with your ability to persuade people. They instead affect follower NPCs. Apprentice ranking will make them wait longer for you, Expert nets you 1 extra follower, and Master allows you to recruit any follower NPC regardless of reaction to alignment. In other words, you can have 2 CP in Persuasion and be an apprentice and yet have less of a chance at altering Loghaire's thinking (extreme example) than someone who has 5 CP in Persuasion yet is untrained. Again BTW, 2 to 3 points in Persuasion is about all you need to get people to spill whatever it is they are holding back; rarely is 4 or 5 needed. Occasionally it is a matter of intelligence or something else that holds your dialog down, but usually it's charisma/persuasion.
What I meant was two levels is deefinately not enough. I also just tried (since my last post) three early on in the game (Between BMC and Despair) as a test and that turned out not to be enough of either levels or time.