The problem is usually caused by proxy / firewall that interrupts the communication between the Adobe Reader/Acrobat and the authentication server.
Why proxy servers affect the process:
Proxy servers are designed to protect your organization from unwanted viruses, malware and other phishing type schemes. However, some types of communication is warranted, such as the content you're trying to access from a legitimate and trusted source.
Proxy server required configuration changes:
- The proxy must ALLOW direct communication
- With the DNS address api.protectedpdf.com and docs-ca.vitrium.com
- On ports 443
Firewall required configuration changes:
- Remove any blocks in Norton or other firewall software for
- The firewall must ALLOW communication with
Adobe Reader/Acrobat Trust Manager configuration changes:
- Open Adobe Reader/Acrobat
- From the top menu bar, select Edit > Preferences
- Under Categories, click Trust Manager
- Click the Change Settings button
- Remove any blocks to https://api.protectedpdf.com/ or https://docs-ca.vitrium.com/
- Allow communication with https://api.protectedpdf.com/ or https://docs-ca.vitrium.com/
How to check for a proxy server:
- Click on the Start Menu and open Settings
- Select Network & Internet > Proxy
- Under Manual proxy setup, check to see if the "Use a proxy server" box is selected
- Content providers have the option to use their own domain name. In those cases, you should contact your content provider and whitelist their domain name instead.
Adobe Reader/Acrobat screenshot