Some of these designs have a special fitting
that runs up the second furler extrusion slot on a halyard, requiring a downhaul. Once they engage with the upper swivel, the sail is loosened and can come down.
Do you have a fancy piece of metal on the boat that you don't know what it's purpose is? And that has a long piece of thin line on it?
To raise the sail you engage the fitting on the halyard with a downhaul on the fitting. The fitting goes in one slot, the sail in the other. Raise the sail, the fitting clicks it in at the head (up top) and use the downhaul to pull the fitting down. To drop the sail, reverse the fitting in the slot, raise it to release the sail.
That's what we had on our boat when we bought it, the system failed and I replaced it, when we redid the standing rigging, with a ProFurl.