I want to monetize my videos, but I was disapproved for being under 18

The minimum age requirement to participate in AdSense for YouTube is 18 years. If you have submitted an AdSense for YouTube application through YouTube Studio and were disapproved by our system for being an underage publisher, your YouTube channel will still be linked to this disapproved AdSense for YouTube application. You should follow the instructions in the disapproval e-mail you received to verify your age (if you are over 18) and resubmit your application.

In case you are under 18 years old, the only way to start monetizing your videos is to link your YouTube channel to an approved AdSense for YouTube account (of a parent or guardian who is over 18).