The Riva logs may contain this error:
Connection to CRM Server failed: Unable to match a user to impersonate by email address: firstname.lastname@example.org
The Riva sync requires matching a user's mailbox email address to the corresponding CRM user's email address.
If the system cannot find a UNIQUE match (whether none or multiple matches are found), then it is not possible to bind a relationship between the corresponding email user and CRM user. In that case, the sync cannot take place and data cannot be exchanged.
Cause of the Error
The "Unable to match user to impersonate" error can occur for one of the following reasons:
Modify the CRM data to ensure that only one active CRM user account is assigned the matching email address value as the target email system user that cannot be matched.