I have a shop that I signed up for tonight that is still pending. I emailed and called the assigner, but now that it is past five should I assume I’m not going to do it?

Well, untill it's in your Assigned Shops, there's nothing really you can do about it, except contact the schedulers again and ask them to do it the following day. It's much better then doing the shop and then realizing it was never assigned to you at all.