you have to guess the authority here
permissions not found

This plugin has no permissions.

Sorry wrong plugin i mean PlayerList and this Works

Without any details, it's hard to really say what the issue may be. If a permission is "not found" though, that generally means the plugin is either not loaded else the permission is being typed wrong. I'd suggest checking your oxide/logs for errors, verifying the plugin is actually loaded, etc. If you still have issues, please use the plugin's support section and provide details.