VirtualNetwork Gateway Public IP Address name won't Resolve

Hi,

I've created a site-to-site VPN, for that I've created a Virtual Network Gateway with a Dynamic Public IP Address. I see that it is required to be dynamic IP, which I believe won't change unless I remove the Gateway manually, am I right?

In this case my issue is, I've assigned a name to this Public IP Address like mycompany.westus.cloudapp.azure.com, but when I try to nslookup this address it will return 255.255.255.255 mean not resolved. I tried it twice and same thing happened again. 

So far I configured my router to work with the IP, but I think it is better to use the name, so can you tell if I'm doing something wrong?

Thanks,

Sadjad Bahmanpour