Found the white threaded cap, removed it, the chrome colored value was in line with the hose coming out of the tank. I turned it so it was perpendicular to the hose.
You closed the valve. Valve is closed with handle perpendicular, open with handle in line. So I'm guessing your tank is empty.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10