If the valve doesn't respond to some silicone spray lube (or even WD 40) replace it.
These are $20 valves and held together with 4 bolts. Should be nearly obvious how to replace it. Tip: buy the new valve before removing the old one. Tip 2: be prepared for a mess when you remove the valve.
2006 Roo 23SS behind a 2017 Ford Expedition