So I called Odahviing to Dragonsreach Great Porch and then used Dragonrend, but when I hit him with my battleaxe, it does not damage. In fact, the little bar on the top that normally shows up that shows an enemy's name/health isn't showing up at all? Why is this happening and how do I fix it?

Woah! Stop attacking him, youre supposed to be luring him further in towards the door so that the trap will trigger.

Why exactly are you trying to hurt him at this point?

Ohh! I see, I forgot all about the trap.

Oh, and welcome to the forum. Heres your http://www.uesp.net/wiki/General:Fishy_Stick!

Hehehe, thanks

Odahviing is flagged 'Invulnerable', thus cannot be hurt. The whole point of the encounter is to trap him, so they made sure that was the only option. It would have been nice to have the option to subdue him through force, though.

Another D'Oh moment.