If you receive the error message, “This email address is not authorized to view this email,” the email you're trying to read was likely sent to an address other than the one associated with your inbox.
Virtru emails can only be decrypted by the specific email address to which they're sent. If an email is sent to an alias address, group address, or is unsecurely forwarded to you by another user, you won't be able to decrypt this message, given the following exception:
Organizations who Have Performed a Domain Sync with Virtru
Users on G Suite domains who have Virtru installed at the domain level or users who have performed an Active Directory sync with Virtru will be able to access and decrypt emails sent to aliases and groups. If you have performed a sync with Virtru and still encounter this error, please ask your admin to double check the last refresh date on the Overview page of the Dashboard. G Suite orgs can refresh the domain’s information with Virtru by clicking Refresh Now on the Overview page of the Virtru Dashboard. AD synced orgs can refresh the sync by an admin restarting their provided AD sync service.