sorry you are not having any luck.

Any backstory or people/groups you may want to reach out to for more help in finding him?
What hobbies does he have? Where does he spend his free time? Drugs or other things that may have caused him to wander off or go into hiding?

Have you been able to hack his social media to get ideas of what was going on or where he has been hanging out?

just trying to brainstorm some ideas that may help you.

good luck and keep thiking positive!