Check for the gasket fit where the pivot spindle crosses .
I think it's possible for the float arms
to hang up on the gasket .
the gasket may need to be clipped back at the corners as shown in the image
Another thing is the tickler roll pin .
It's adjustable , as a friction fit , and may have adjusted itself by accident
if it is set too low ... the float cant float .
... if it's set to high the tickle does not tickle