You've disabled the search feature of your forum. The search plugin works.
You don't need to run nodebb upgrade when installing plugins. Nor do you need to disable it either. Nodebb reset plugins switches off all of your plugins.
Go into your ACP and switch your installed plugins back to Active, restarting NodeBB each time until it crashes, post here the full crash log (looking for the name of the plugin), chances are their will be an update for it. To update a plugin
That's all you need to do, you don't need to upgrade or update. Go into your ACP and reload your forum.
Only do nodebb upgrade when you pull the latest files. And don't reset plugins unless you're having an issue with plugins and you don't know which one. to disable a specific plugin, ./nodebb reset plugin="nodebb-plugin-name"