SSL Certificate couldn't be provisioned

-Hi, my Netlify site name is pcworldke.netlify.app
-I’ve used a custom domain pcworldke.co.ke for it, which I acquired from hostafrica.com
-The DNS propagation seems completed after using netlify nameservers
-My issue is that when I proceed to use the SSL/TLS certificate option, I’m faced with the error "We could not provision a Let’s Encrypt certificate for your custom domain.
-I don’t exactly know where the problem is.
-Can I get some help to resolve this please?
-Thanks in advance.