Unable to connect via RDP to a Azure VM after its size is changed from small to medium

I had changed an Azure VM size from "small" to "medium" after which I am unable to RDP into it.

I tried the following steps without any luck:

- Deleted the VM by retaining the OS disk and created a new VM from the same disk

- Delete and re-add the RDP entry in end points

- I also created another VM and tried connecting via RDP from it using the internal IP address

I am also observing a weird behavior where the "HOST NAME" property shows as "-" for the VM in question. 

Note that the VM itself was created from the "Windows Server 2012 Data Center" image available in the Azure Portal.

Appreciate if anyone could help or provide some pointers to resolve this?

Thanks for your help in advance!