A plugin failed to load
Applies to Paper, Vanilla.
What it looks like in your log
Could not load 'plugins/MyPlugin.jar' in folder 'plugins'
What causes it
The server could not load a plugin jar.
How to fix it
Check the lines just below the failure for the reason, and swap the plugin for a build made for this server version. If it keeps failing, remove it.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log