Hi @Mayank Sing,
Thanks for contacting Microsoft Q&A platform.
To allow a user to log in to the VM over RDP, you must assign the Virtual Machine Administrator Login or Virtual Machine User Login role to the resource group that contains the VM and its associated virtual network, network interface, public IP address, or load balancer resources. Can you try this adding the user to the resoure group and other associated dependencies.
Hope this helps you.