Vaper’s tongue is can refer to a variety of different complaints among vapers. It can be as simply as no longer being able to taste your favorite flavor of e-liquid properly, to experiencing all food/drink and e-liquid flavors as being very muted.
Vaper’s tongue is most commonly attributed to vaping the same flavor for too long (desensitizing the user to that particular taste). The fix here is simple, vape something different every once in a while.
Certain actual medical conditions can also lead to loss of taste sensation, if you’re experiencing this and it does not rectify itself fairly soon it might not actually be ‘vaper’s tongue’ and may be worth going to a doctor and seeing if there is another cause.