Contracts advancing

I've never run a league with contracts before, but I decided to test it out in my Sandbox league. However, when I progressed players, the contracts didn't progress. They are still signed for the same amount of time as originally. I haven't been in a contract league for a while, but if I remember right, when a player with a 1-year contract was advanced, it changed to one "$" instead of two "$$". However, that didn't happen to any of the players. Does it not work because it is a real progression league? (I've never seen a contract league for real progressions). Or did I fail to do something during progressions?