Error was received when trying to add a secondary domain, "Error: Primary and/or secondary domains must include at least one value which matches the current user's domain.
The primary domain had not been configured for the tenant yet. The logged in user's domain did not match any of the domains that were listed on the tenant
Follow the directions in the tech note "Setting up CloudSOC cloud services" to configure the primary and any secondary domains.
If your primary domain has already been configured then follow this document "How to manage secondary domains in CloudSOC"