"Allow only secure FTPS connections" is set in Tools & Settings > Security Policy, but secure connection fails below errors can occur for different FTP clients:
CONFIG_TEXT: Insecure server, it does not support FTP over TLS.
CONFIG_TEXT: 534 Policy denies SSL
CONFIG_TEXT: Local policy on server does not allow TLS secure connections
Settings for FTP site were manually changed in IIS.
Note: This article can be applied only if you have an administrator access to Plesk. Contact hosting provider if you don't have admin access to Plesk.
Reconfigure FTP site:
- Log into Plesk
- Go to Tools & Settings > Security Policy and set Allow both secure FTPS and non-secure FTP connections > Apply
- Set Allow only secure FTPS connections > OK