Your atty may be dry. Either the cart filler is not touching the bridge on the atty (depressed back into the cart too far) or the cart filler is stuffed way too tight (compacted) and not wicking into the bridge.
A quick check for dry atty is to drop 2 or 3 drops of
juice on the bridge and tailpipe the atty (
vape it directly from the tube that the cart slides into). If you get vapor the atty was dry.
I've also had no vapor with a warm atty when the atty was actually flooded. In that case, blowing it out from the battery end into a sink or paper towel and trying again restores vapor. Try it at first with no
juice added after blowing it out.
One of the two states is probably going to be true, dry or flooded. If not, then maybe the coil is crusted over. A good cleaning is in order. Try washing it out under hot water, then blowing the water out and doing a pulsed dry burn until you see the coil glow dull red. Re-insert a full cart and vape for a while until it vapes normally.