The Digital-ID certificate needed to decrypt the message is no longer available to Outlook.
The root cause of the issue can be observed in a client trace while replicating the issue. The following client trace excerpt shows the source of the issue.
AutoWrap() IDispatch::Invoke("Display"=0000f0a6) failed w/err 0x80020009 [Your Digital ID name cannot be found by the underlying security system.]
Explanation
When a request to open a shortcut is issued by the user, the EV Outlook Add-ins capture the request. The archived item is then downloaded to the local machine and a request for Outlook to open the item is made. During this process Outlook attempts to locate the required Digital-ID certificate to decrypt the item. When Outlook is unable to decrypt the item, the error message seen above, is returned to the EV Outlook Add-ins. Once the message is returned to the EV Outlook Add-ins, the message is then displayed to the User.
Locate and install the correct Digital-ID certificate.