Unable to connect to Virtual machine suddenly via RDP through public IP

Since restart, Reset configuration only, redeploy, NIC reset, multiple laptops, and multiple networks were already tried, the next supported checks are the remaining Azure RDP troubleshooting steps:

1. Verify Network Security Group rules again with diagnostics, not only by inspection
   • In Azure, use IP flow verify to confirm whether an NSG rule is blocking traffic to the VM.
   • Also review effective security rules on the NIC/subnet and confirm an inbound Allow rule for TCP 3389 exists and has higher priority than any deny rule.
2. Check whether the VM is reachable on the network path
   • From a machine in the same network, run:

          Test-NetConnection -ComputerName <public-ip-or-name> -Port 3389 -InformationLevel Detailed
     

   • If TcpTestSucceeded is False, the issue is still network-path related.
   • If TcpTestSucceeded is True, focus on guest OS configuration or authentication.
3. Review VM boot diagnostics
   • In the Azure portal, open the VM and review Boot diagnostics screenshot/logs.
   • This can reveal startup problems that block RDP even when the VM appears running.
4. Check VM Resource Health
   • In the VM blade, open Resource health.
   • A healthy VM should show Available.
5. Verify routing
   • Use Network Watcher Next hop or review effective routes to confirm no route is preventing traffic to or from the VM.
6. Confirm outbound TCP 3389 is not blocked outside Azure
   • Since multiple laptops and networks were tested, this is less likely, but any on-premises firewall or local firewall still must allow outbound TCP 3389.
7. Check guest firewall if console access is available
   • On the VM, verify Remote Desktop - User Mode (TCP-In) and Remote Desktop - User Mode (UDP-In) are enabled.
   • Elevated PowerShell:

          Get-NetFirewallRule -DisplayGroup "Remote Desktop" | Set-NetFirewallRule -Enabled True
     

   • For testing only, firewall can be temporarily disabled:

          Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled False
     

   • Risk: disabling firewall reduces protection. Re-enable it after the test.
8. Check DNS vs IP behavior and RDP port
   • If connecting by hostname fails, try the public IP directly.
   • Verify the VM is still using the default RDP port 3389. If the port was changed, connect as IP:port.
9. Reset the VM password if credentials may be involved
   • In the Azure portal, use Reset password if there is any chance the local admin credentials are incorrect.
10. If all checks still fail, open a support request

• The documented guidance is to open a support request after these steps if RDP issues continue.

A common Azure-specific cause when RDP suddenly stops through the public IP is that the VM no longer has a usable public IP association. If the Connect button is grayed out and there is no ExpressRoute or Site-to-Site VPN, assign a public IP to the VM NIC/IP configuration before using RDP.

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