Plesk Server FTP Issues

I maintain several VPS servers for clients at different hosting companies. Recently, a VPS at 1and1 would not allow directory listings through FTP access. I checked the logs and noticed Plesk had updated to Onyx Version 18.0.24 in the past few weeks so started perusing online forums for known issues.

ProFTP configuration settings and install issues popped up in online help forums as well as firewall ports necessary for FTP. I had attempted several of the fixes as well as checked the Cloud VPS firewall and even went as far as adding rules for additional ports based on the forum threads. However, nothing I attempted corrected my issue.

FTP had been working perfectly for several years so I then dug into the Plesk firewall and although there were no changes to the configuration - the following rule added to the config allowed directory listings again.

TCP/UDP ALL - Ports 30200-30400

Saving and restarting the firewall got everything back up and running. Not sure why the update required this additional rule that was unnecessary before but hopefully will help someone else looking for an answer.