Gas Flow - Abbey Adventure 325

Hi I have an Abbey Adventure 325.
My gas connection is good on gas bottle & when first connected I get gas to my cooker.
When not used for a little while when I try to use the cooker there is no gas coming through.

There is some sort regulator between rubber pipe & metal pipe with a little yellow button sticking out on the side.
Does this button mean it blocked or needs changing & that's what is affecting the gas flow.