New class on same character.

[Urielparadox]

I highly suggest reading the action help menus that pop everytime you get certain things accomplished. If you had you would know what to do here.

A quick google search of the 2 words "ff14 thm" yields a first result of
http://ffxiv.gamerescape.com/wiki/Thaumaturge
which has a list of all the quest and what you need to do.

[TheCurls]

I highly suggest reading the action help menus that pop everytime you get certain things accomplished. If you had you would know what to do here.

Not helpful at all. Why are you in the new player help forum?

To the OP, did you get the THM weapon from the end of the first quest, or did you equip one you had bought? If you equipped one you had bought, try taking the quest as paladin, then completing the quest by going from the receptionist to the guildmaster. The quest reward will give you a weapon, in which case, any THM weapon you equip will register for the next quest from the guildmaster.