I signed up for Global Entry and once I was approved it said that there were no appointments at all. How is that possible?

What is the regular process?

I've also seen people have luck (at RDU, at least) by waiting outside the office to see if they can work you in. Appointment slots are for significantly longer than they usually take, so there are often big gaps in their day.

Because the terminal backlog and lack of TSA agents, it's best to go through the regular process until manpower is caught up