As above, re calibrate it
If its the digital ian sheppard jobbie, then press and hold up and enter until 'cal' shows up
Scroll all the way down to 'aut'
Press enter
After a few seconds a number will show, press enter again
Jon jobbed
You should (ideally) do all that with the water flowing, pole extended and a bit of hose reel pulled out
Wont be air in the system, usually the flojets rattle like a moped rather than pulse when there's air...