Do you have any bubbles in the line between the proportioner and your pump? Squeeze trigger and watch that line. If you see air bubbles in fluid before pump, your getting air in your system. Mine is fed with 1/4" soap, 1/2" chem and water line to proportioner, 5/8 from proportioner to pump, 5/8 from pump to reel and then 1/2" on reel. Mine shoots 37’
Make sure all your lines are in fluid when testing. I couldn’t figure out why I was getting air for the longest time. I would open water and chem lines (chem was in water too for testing) but I left the soap closed. Here the Pentair valve was still pulling the tiniest bit of air through the system despite being closed, Dropped the soap line in a bucket of water and problem solved. Pulled water instead of air. Air wrecks performance real quick.