Plex does not have the "Send Messages" for the channel. Give it the permission and it should work.
Lag. Sometimes Plex takes a while to respond to commands (this happens mostly with commands that require a database).
Plex is offline. This can happen when the bot is down for maintenance or if our hosting provider is down. Join our Discord Server for updates on new features and downtime.
Slowmode. If this happens, give Plex the "Manage Messages" permission. Plex will then be immune to the slowmode.
If none of these methods work, send us a message in the #support channel on our Discord Server.