Signing up for multiple rematch Santas?

This is my first year participating in RSS, or any reddit gift exchange for that matter. My experience as a Santa has been great. My experience as a giftee has been a bit frustrating, but oh well. Got shafted by my original Santa who only pulled my info on match day and on shipping day. Got rematched, and my rematch actually sent me a message at one point, so I'm hopeful.

I signed up to be a rematch Santa, and have since shipped out to my giftee. As it's my first time, I could only sign up to be 1 rematch. The packages arrived yesterday to my rematch giftee and I was going to see about signing up to be a rematch for someone else. It doesn't seem to be letting me though. Can I not sign up to rematch again until the current rematch giftee posts their gift?