Error on Acquia Cloud while adding a domain

Issue

You are trying to add a domain on Acquia Cloud and receive the error:

An unknown error occurred. Please try your request again. If the problem persists, Contact Acquia Support. Request Id: xxxx

Cause

This can occur if you have another Acquia Cloud application where the domain is already in use. A domain can only be used for one application at a time. 

Resolution

You will need to remove the domain associated with the other application before adding it to the desired application on Acquia Cloud. This process is typically quick and, by setting a higher caching time or utilizing a CDN, the impact to visitors can be reduced.