Can't install Acronis Backup in Plesk: Failed to connect to host "45.11.1XX.XX" via port <port_number>

Symptoms

• Acronis Backup fails to install, and returns this error:

  Failed to connect to host "45.11.XXX.XX" via port <port_number>.
  Please update your firewall configuration and restart the installation.

  Note: the IP address and port may vary

• Connecting to the IP address from the error using telnet fails:

  # telnet 45.11.XXX.XX <port_number>
  Trying 45.11.XXX.XX...
  telnet: connect to address 45.11.XXX.XX: Connection refused

Cause

A temporary issue on Acronis CDN.

Resolution

Wait a few hours, and try to install the extension again. As a workaround, point the Acronis URLs to their IP address locally.

1. Connect to the server via SSH

2. Add the following lines to /etc/hosts:

   45.11.XXX.XX eu2-cloud.acronis.com
   45.11.XXX.XX eu2-cloud.acronis.com
   45.11.XXX.XX eu2-cloud.acronis.com

   Note: replace the 45.11.XXX.XX placeholder with the actual IP address mentioned in the error message

3. Install the Acronis Backup extension again