app service managed certificate error

Question

I'm encountering managed certificate creation error. I have tried with various domains, including both top-level and subdomains. I have configured the A record and ASUID TXT record properly (propagated successfully as we waited days). The domain validation succeeds, but it fails every time during the certificate issuance process. I also tried adding a CAA record for Digicert (as per this forum: https://learn.microsoft.com/en-us/answers/questions/630305/cant-create-ssl-certificate-for-a-dns-with-top-lev) but had no luck. We tried every possible way to solve the issue but keep getting the same error.

Before, I've added 251 domains and all SSL were generated and bind successfully.

here is error message is showing on creating ssl,

"Create App Service Managed Certificate and configure SSL binding
Failed to create App Service Managed Certificate for chuanparkshowflat.com due to error: Pending managed certificate failed: Certificate creation failed unexpectedly for canonical name chuanparkshowflat.com. Contact support for assistance. Refer to the documentations for more info: https://go.microsoft.com/fwlink/?linkid=2158627.
"