In occasional instances a P11D Organiser installation can fail to activate, and the message that comes back relates to the 'Revocation Server'. This is the server that handles the authentication of the SSL certificate, and even if a firewall is correctly configured to check the server ( marked as insecure or having invalid certificate), it appears that Windows can either cache or retain old information - this is also user profile based on a Windows PC/server.

To correct this:

  1. Type in Internet Options in the Windows menu
  2. Pick the Advanced tab and then scroll down to the Security section as shown below.
  3. Then turn off or uncheck Check for server certificate revocation, again, highlighted below.
  4. Click OK at the bottom of the window.

Technical Details

The underlying issue with this error is that a machine is being blocked from contacting the revocation servers for our web server's SSL certificate. To pass the check a machine needs to contact at least one revocation server over an HTTP/port 80.