For the information about how to back up Plesk running on a Virtuozzo container, refer to the 
"Installing the backup agent on a Virtuozzo host" (p. 14) section or contact your service provider. 
To back up Plesk running on a virtual or physical machine, you need to have an account in the backup service. 
Adding your plesk server in to the backup portal. 
- Go to Server Management > Acronis Backup. 
- Click I have an account. 
- Specify the backup service URL and the credentials of an account to which the machine should be assigned. 
 This account must be created within a customer tenant (Customer administrator, Unit administrator, or User). Do not specify the credentials of a partner administrator.
- Click Sign in and enable, and then Enable. 
 
To enable backup after reinstalling the extension or Plesk 
- Go to Server Management > Acronis Backup. 
- Specify the backup service URL and the credentials of an account to which the machine is assigned. 
- Click Sign in and enable, and then Enable.