Could be a number of things.
It could be a bad cartomizer. Certainly would not be unheard of. The quality control of many manufacturers leaves much to be desired, especially if they are the cheaper no-name brands. There are also reports of knock-offs being sold as a name brand carto.
Not my intention to be insulting, but since you do have a low post total, I can only assume you are relatively new to
vaping and cartotanks.
Is your cartomizer in your tank "punched"? (hole for the
juice to wick from the tank into the cartomizer)
Did you fill the cartomizer properly with
juice before assembling your cartotank and then filling the tank itself?
What is the pg/vg ratio of the juice you are using. A juice that is very thick, like AVE's Boba's Bounty is 100% vg, can be a real challenge to use in a cartotank.
Did you view any demo videos on how to fill a cartomizer and assemble/fill a cartotank?