Only thing I can think of if you haven't already is making space in the inv and going back to talk to the last quest guy.
Most quests will not allow you to complete them if have a full inv. So, even if you think you have finished go back and talk to the final quest dude again. Failing that, try and do just the last part of the quest by talking to the second last quest giver.
Being new quests however, they are probably bugged and this won't do anything for you.. sorry :(