Auto matic shut off

\015 When the recovery tank is full the yellow float disc is supposed to rise to the top of the tank lid… it does not. other than that, the machine is working fine…..Ever since I hooked up the hose and attachment to clean some upholstery, now that I am back to cleaning carpet.. I have this issue with the yellow disc\015 – Hoover F5912-900 Upright Steam Vacuum