Seaclo Repair Kits
You might need one of these.
Occasionally, after lack of use, I need to do several short rapid pumps to get water flowing.
( priming the pump so to speak)
There's a little rubber gasket around a plastic ring at the end of the plunger that wears out and may not be allowing proper suction.
I had one unscrew itself once..guests kept spinning the handle...does the plunger feel loose?
I purchased the above kit a few years ago and it made a world of difference, worked like a brand new head!