A certificate might be rejected during the application process. We will keep trying to rectify the problem during application, and contact you if we are not able to resolve it without assistance.
A certificate can also be revoked after issuance; if for instance, the site is marked as non-secure owing to hacking or some other unforeseen event.
If you have any problems with rejected or revoked certificates, please contact us with your DNS details and the domain(s) impacted, so that we can assist you.