First check your lines are connected, CO2 tank is full, turned on and the regulator is set correctly. Regular cleaning and maintenance is a key factor in safe guarding the quality of the dispensed beer.
Beer lines have to be periodically cleaned because of crystallised build up which forms on the firrings, lines and taps, commonly refereed to as beerstone. If beerstone is not completely removed in a cleaning process it will leave an unsanitary surface that can harbour microorganisms which will cause undesirable flavour and cause the beer to become over carbonated or become flat and lifeless in the glass.
Sufficient beerstone will also lead to dispense problems.
To start of with we recommend to rinse the lines with water after each drinking session. this helps to preserve the beer lines.
Purchase and follow the directions of a liquid line cleaner. ensure to thoroughly rinse the lines with water after cleaning. fully disassemble the tap and clean during this process.
If you still experience issues, with another kegs that the ball locks engage properly. You might have some hop's blocking the keg dip tubes.
Very important not to apply force to move the handle , as it will most likely lead to damage in the handle/tap.