I don’t think you own subdomain.mydomain.com 
.
It’s possible that if the domain is newly registered it’s not propagated DNS.
But I can’t think of anything obvious without going down a “what if” hole of firewall ness or misc
I don’t think you own subdomain.mydomain.com .
It’s possible that if the domain is newly registered it’s not propagated DNS.
But I can’t think of anything obvious without going down a “what if” hole of firewall ness or misc