Is tank empty?
You might be out of CO2; replace your CO2 Carbonator by exchanging it for a full SodaStream 60L CO2 Carbonator. If you have a Mini CO2 carbonator installed: bring your empty Mini CO2 Carbonator to a participating retailer and swap it for a FULL 60L Carbonator.
Is there enough water in the bottle?
Check that the carbonating bottle has been filled up with water to the fill line.
Is the tank on correctly?
CO2 Carbonator may be loose. Do not use tools. Detach the bottle, open the rear cover, and retighten the CO2 Carbonator. Apply firm pressure but do not overtighten. If the CO2 Carbonator is already firmly in place, it may be empty.