Uploaded Certificates cannot be renewed by Cloudflare. You must ensure that you replace an expiring certificate before it expires, otherwise your visitors may not be able to connect.
Cloudflare automatically sends email notification 30 and 14 days before your custom certificate expires. Email is sent to users who have the SSL/TLS, Administrator, or Super Administrator roles.
Expired certificates and Legacy Client Support
For Modern custom certificates, Cloudflare removes expired certificates at expiration. Affected domains and subdomains will fall back to any other active certificate covering the hostnames on the expiring certificate.
For Legacy custom certificates, Cloudflare will remove the certificate 24 hours before expiration if a valid replacement is already available. If no valid replacement is available, Cloudflare will remove the certificate 30 minutes before it expires.