Same problem again...
Actions that I have made to 'fix' this problem:
Disable single plugin ./nodebb reset plugin="nodebb-widget-essentials" - No Success
Disable all plugins - No Success
Drop all collections in Mongo, and ./nodebb setup - No Success
Delete nodebb.min.js from public directory - No Success
Delete all public subdirectories that could be found in .gitignore - No Success
Delete public directory and checkout latest from current branch - Success
Maybe it will give you some insights
I know this is quite old, but i encountered the same problem. I had localhost written in my config.json, but changed it to my domain. I still get GET http://localhost:4567/plugins/nodebb-plugin-emoji-extended/images/smile.png net::ERR_CONNECTION_REFUSED
I also restarted my server with the admin gui - is a hard restart or reinstallation necessary for the changes to take effect?