A few people have had an issue with the pre-filled clear co2 cartridges where a small air bubble develops around the wick at the base of the cartridge. This prevents the wick from absorbing any more oil and makes it difficult to get a proper medicated drag. Luckily there’s an easy fix. Remove the mouthpiece of the cartridge, if it’s metal then it’s likely a twist off (it might be a bit stuck, but it will come off). If it’s plastic, it’s likely a snap off mouthpiece. Beneath that there’s a little blue rubber stopper that seals in the oil. Remove and replace that piece several times. Every time you replace it, the seal will force air pressure on the oil, pushing it down onto the wick. Replace the mouthpiece and you’re all set.