Weak flavor does not always mean you need a new device. Start with the coil, power, airflow, and liquid. If those are normal, your own sense of taste may simply need a break from that flavor.
Check coil age and residue
A coil can lose clarity before it tastes burnt. Sweetener and flavor residue cover the heating surface, turning distinct notes into a flat background. If the same coil has been through many refills and cleaning the tank does not help, replace it.
Prime the replacement fully so you do not trade muted flavor for a burnt wick.
Return to the correct power
Power below the coil's range may produce cool, thin vapor. Begin at the lower printed setting and move up gradually. Stop when flavor becomes clear; more power eventually adds heat without adding useful detail.
Adjust airflow in small steps
Very open airflow dilutes and cools the puff. Closing it slightly may concentrate flavor, but closing it too far can overheat the coil. Make one small adjustment, then reassess the wattage.
Remove the previous liquid
A strong mint, tobacco, or dessert flavor can linger in a tank and muddle the next fill. Wash the empty tank parts that the manufacturer identifies as washable, dry them completely, and install a fresh coil when changing between very different profiles.
Check storage
Heat, light, and repeated exposure to air can change e-liquid. Compare the bottle with a fresh one if it has been open for a long time, smells different, separates, or has changed texture.
Flavor fatigue is real
Using one flavor continuously can make it seem less noticeable even when the device is working normally. Drink water, take a break, and compare a different familiar flavor in a clean setup. Do not keep raising power to chase a taste your senses have temporarily tuned out.
See why juice tastes different between coils for the hardware side of the comparison.