You retain all your certificates and access to them. You can still edit, remove and monitor your certificates. The only restriction is that you're not able to create new certificates.
Any certificate that you have issued on Accredible does not get deleted.
Your credential recipients will always be able to access a certificate they have received. Even if you stop paying for your Accredible account, your credential data will be preserved in case you come back to your account at some point in the future, and to maintain support for your current credential holders.