Toilet won't flush when not connected to city water?

[Ddoyle2]

We have only made three trips so far in our 2014 Minnie Winnie and have always connected to a water system at the camp grounds.

So now I want to go dry camping so I have filled the clear water tank. Sinks and shower all work but the toilet is not getting any water? The instructions mention turning a water valve to system use but I can't find this water valve.

Can anyone tell me where I find this hidden valve or if there are other suggestions as what the issue might be.

Thank you,

Don Doyle
Glendale, AZ.