When a custom domain is added in Bubble, it takes Cloudflare some time to work through a backlog queue to validate the certificate. Cloudflare requests two certificates per domain from their default SSL provider, Let's Encrypt. Let's Encrypt has a limit of five certificates per domain per time period.

If, during this waiting period, there are several requests in a short period of time to delete and create the domain, then the certificate issuer (Let’s Encrypt) will rate-limit issuing certificates for that domain. This rate-limiting delay results in taking even longer for Cloudflare to validate the certificate. We have to wait for the rate limit to expire and then for Cloudflare to perform the validation. If your domain is being rate-limited, you will likely see the error 403 Cloudflare Forbidden when accessing your domain.

Please do not attempt to make changes to your domain during this time. Once the rate-limiting expires, Let’s Encrypt will be able to issue your domain the SSL certificates for Cloudflare to validate.