Do you have to be the same level as the quest? I've been at least the same level, but it's possible that I've been higher than all of them, if that would stop me from being able to do them

Do you already have an active quest?

I ran into the same thing and I think I had an active quest that was preventing me from picking up others.  Once I completed the quest I had, I was able to pick up others.  Not sure if that's how it's supposed to work or maybe I finally met the criteria for the quest?  It was a late night so I don't guarantee the recollection of what I did last night.