This is an uncommon error which can occur when there’s an issue with OCSP stapling on your webserver. It happens when OCSP stapling is required, but not available. We recommend to contact your hosting provider about this issue, they will be able to enable OCSP stapling which will fix the issue.
The other reason this error can occur is if you are behind a proxy. If that is the case, you can try the following to access the site:
- Paste about:config in your browsers address bar
- Enter ocsp in the search field
- Click on security.ssl.enable_ocsp_must_staple and change the value from true to false