The email address that is used to activate the Securlet must match the email address of the user in Salesforce.
Verify that the user logged in to the CloudSOC tenant is a System Admin on the tenant.
Verify that the CloudSOC admin and the SalesForce admin emails match. It is important to remember that:
"Salesforce user IDs sometimes may look like email addresses such as [email protected] or [email protected], but they are not email addresses. The user account has a separate email address field which may sometimes be the same as user ID."
Update the user's email ID in Salesforce with the appropriate domain.
In Salesforce, go to setup > users > update users email ID.
Documentation for activating SalesForce