OP, your post title makes it seem he just forgot to register. Here's the original tweets...

So my registration to Vote here in Maryland didn't go through. I was pissed. I checked it out and turns out I am still registered to vote in Arizona. SO I JUST BOOKED A FLIGHT AND I LEAVE IN 2 HOURS.

In case there was any doubt. I will be voting for @realDonaldTrump