In order to ensure Virtru senders can revoke and expire their secure messages whenever they'd like, Virtru requires a constant, stable internet connection to display your secure messages. The decryption keys are actively passed to the reader while the message is open, and are pulled back as soon as the message is closed. If the connection is severed, the keys become unavailable to the reader and the message is locked.
Some users may encounter the above error when viewing a secure message in the Secure Reader, despite having a steady internet connection. If that's the case, the error is likely caused by a security device blocking access to a required Virtru Endpoints. With these servers blocked, the Secure Reader reacts the same way it would if the internet connection was fully severed.
To solve this issue, please whitelist the URLs found here with your network security tools.