Unable to set IP address xx.xx.xx.xx for hosting in Plesk: it is already used by another account.

Symptoms

• Changing the IP for a domain via CLI results in the error:

  # Unable to set IP address xx.xx.xx.xx for hosting: it is already used by another account.

• Trying to create a domain via API causes the error:

  # Unable to create hosting. Ip address does not exist in client's pool.

• There are no Resellers configured on the Plesk Server.

Cause

The IP address is set as 'dedicated' type at Tools & Settings > IP Addresses.
This prohibits it from being assigned to other domains.

Resolution

Follow the steps on article: How to change IP address type in Plesk? and set the desired IP address as Shared.