Yep have a 24V AC output adaptor and it is opening and closing the valves fine now. Just confirming for any other people in the future that might find this thread after having the same issue – check your adaptor 🙂
A DC adaptor makes the Opensprinkler look like it’ll work because it starts it up fine and opens the valves but it needs the proper AC adaptor to open AND close them, which is kind of the useful part of the sprinkler system 😀