Most common:
Lack of vapor can be from too much or too little liquid.
Too little and you would have probably had burnt taste as your clue...so you need more liquid at the coil.
Too much and you might hear gurgling... The coil is quite small and while it can vaporize a small amount of liquid, it simply cannot vaporize a whole pool of it... Try gently blowing
through your atomizer into a sink or paper towel to get the excess liquid out.