Why SSl is using certificate of another subdomain!!!

Hello


Thanks for your attention.

I have created a new subdomain, word.website.com, but when I want to use, it it says:

"Your connection is not private
This server could not prove that it is word.website.com; its security certificate is from www.blog.website.com. This may be caused by a misconfiguration or an attacker intercepting your connection."


And when I use Cloudflare it says Error 526: Invalid SSL certificate

Or at the first try word.website.com; redirceted to www.blog.website.com


What's the problem?

Thanks