This error displays based on the settings within your web browser.  Typically this can be resolved by adjusting the security settings within your browser.

To adjust security settings in Internet Explorer:
  1. Click on the Tools menu and choose Internet Options
  2. Click on the Advanced tab
  3. Scroll down to the "Security" section
  4. Remove the checkbox next to "Check for server certificate revocation"
  5. Click OK
If this does not resolve the issue, try the following in Internet Explorer:
  1. Click on the Tools menu and choose Internet Options
  2. Click on the Security tab
  3. Click on Trusted Sites
  4. Click the Sites button
  5. Add the login URL for FENXT (https://fenxt.blackbaud.com) in "Add this website to the zone:"
  6. Click Add
  7. Click OK
Also ensure that the date/time on your workstation is correct.  This has also been known to cause this error.