The error ‘The revocation function was unable to check revocation because the revocation server was offline.’ is raised when an application is trying to check if the provided certificate is valid but it is unable to connect to the revocation server. The usual cause is that the server is fire-walled and cannot connect out to do the validation.
To see what Url is needed to validate the certificate – Open the certificate and look at the details. We will be looking for a field called ‘CRL Distribution Points’. Now simply add a the url to the allowed list.