macOS Mojave - locate not working
Amigo, I might start with launchctl:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.locate.plist


Then check for any impediments to obtaining exclusive lock privilege on the nonexistent database:

sudo fuser -fu /private/var/db/locate.database
sudo lsof /private/var/db/locate.database


Then kill any process reported by either command.  Next, run the db generator by hand, preceded by an opensnoop for debugging if something goes wrong.  You will need to open a new terminal window ( command key - N shortcut, I believe ) and run opensnoop there, exiting it with a Control Key - c combo.

sudo opensnoop -cegx -f /private/var/db/locate.database 


Then over to your original window type:

sudo /usr/libexec/locate.updatedb


Remember to quit opensnoop with a cntrl-c in its window.  

F.