Keg blocked, probably

[enoch]

first thing.
take to safe place
press softly on the beer poppet

if beer comes out, there is likely a problem in the lines/tap

Do this before any of the harder options.
Putting a tea towel over the top of the keg when you depress the poppet is advised.

 

[Camo6]

And if it is a blocked pickup and you try to cheat by carefully pushing the gas connect onto the liquid be sure to crank up the pressure on the reg first so it is higher than the keg, then remove it before pressure equalises. No one likes beer in their gas lines or reg.