Plesk backup to remote FTPS storage fails: Last FTP request: APPE

Symptoms

• Plesk backup to remote Microsoft FTPS storage fails:
  

  CONFIG_TEXT: Unable to create the remote backup: Curl error: Unable to finish an upload: (28) Timeout was reached: Last FTP request: APPE backup_xxxxxxxx_xxxxxxxxx.tar: Last FTP response: 125 Data connection already open; Transfer starting: Connection to the FTP server has lost

• An attempt to re-enable FTPS support in the remote repository settings fails:
  

  CONFIG_TEXT: Error: Unable to upload the file to the storage: Stream error: /check0/test: Curl error: Unable to finish an upload: (28) Timeout was reached: Last FTP request: APPE test: Last FTP response: 125 Data connection already open; Transfer starting: Connection to the FTP server has lost

Cause 

Plesk bug with ID #PPPM-14635 which will be fixed in future Plesk updates.

Resolution

As a workaround:

1. Log into Plesk

2. Go to Tools & Settings > Backup Manager > Remote Storage Settings > FTP(S)

3. Uncheck the option Use FTPS