Azure VM HOST NAME not registered

Symptom-

1. Finished provision a new VM at Azure portal
2. Join the VM into our domain
3. Restart the VM but no luck with RDP connection

looking at the Portal, we could see that the VM did not registered it's Host Name at all, and it is blank or with status Retrieving, this is why we cannot open an RDP session into the VM.

we already investigate the Endpoint mapper for this VM, and it is set as it should with Remote Desktop protocol with Public & Private ports

does anyone has a solution for the problem or what should we do in order to fix the problem?