what does launchd status 78 mean?? why my user agent not running??

I found the error had to do with permissions. I was trying to redirect errors and logs to the /var/log directory which my user is not able to write to. Changing the path to something where my user had proper permissions to r+w fixed it.

Also, be careful when loading your LaunchAgents. Do not use sudo to load a plist if you are in the ~/Library/LaunchAgents directory.

I read man launchctl, find 78 means function not implemented. It doesn't help much.

Finally I make it work, actually there were errors in the plist, I recommend to install the brew install --cask launchcontrol, which is a gui tool for launchctl, it can help detect errors and trouble shooting.