Unable to setup sub domain with Transip & Azure VM

I trying to setup a subdomain api.mydomain.com in Transip, I can ping mydomain.com but not api.mydomain.com, ping is ICMP is enabled in the VM, This is the scenario:

1. mydomain.com domain works can ping
2. api.mydomain.com can't even ping.
3. both main domain & sub domain point to the same VM.

My api CNAME is somevmw.southeastasia.cloudapp.azure.com. My www CNAME is @

Any help will be appreciated.

Fixed & realised, the Primary Server Name is in correct