How to add custom host names with SSL for SaaS and resolve SSL handshake failed issue

In our organization domain, I want to add a custom host name with SSL for SaaS, and the custom domain is also on Cloudflare. I tried the HTTP and TXT validation methods, and as the document suggests, I added CNAME to the custom domain that points to our organization’s subdomain. but the SSL handshake is failing (error 525). need assistance to resolve this issue.

When looking at the domain we are seeing a 1016 error.
It appears your fallback origin is returning this error.

You will need this record to resolve correctly.

Have you checked our tips on resolving this error?