How to fix 421 Too many connections from this IP with FileZilla
- Launch FileZilla and click File -> Site Manager.
- Under the Select Entry section, choose your site, then tap the Transfer Settings tab.
- Tick the Limit number of simultaneous connections box and fill out the Maximum number of connections field with your preferred amount of connections.
- Click OK to save the settings.
- Reconnect and see if FTP error 421 is gone.