WAC Stuck in starting

First determine whether the browser itself is being redirected to port 6515 or whether 6515 is only a backend listener; do not change the port until its owning process and the WAC service state are identified.

1. Identify which process owns ports 8888 and 6515

On the Windows Admin Center gateway, open PowerShell as Administrator and run:

Get-NetTCPConnection -State Listen |
  Where-Object LocalPort -in 8888,6515 |
  ForEach-Object {
    $c = $_
    Get-Process -Id $c.OwningProcess -ErrorAction SilentlyContinue |
      Select-Object Id, ProcessName,
        @{Name='Port'; Expression={$c.LocalPort}}
  }

Then check the URL shown in the browser:

• If it remains https://<gateway>:8888, port 6515 is not the browser-facing port. Do not modify it merely because it is listening.
• If the address changes to https://<gateway>:6515, the configured HTTPS endpoint has changed or the browser is being redirected incorrectly.
• If neither port has a listener, proceed to the service check.

The modernized WAC gateway uses multiple processes, but that architecture alone does not establish what port 6515 is being used for on this installation.^1^

2. Check and start the gateway service

Microsoft’s gateway troubleshooting procedure requires the ServerManagementGateway or Windows Admin Center service to be running.^2^

$svc = Get-Service -ErrorAction SilentlyContinue |
  Where-Object Name -in 'WindowsAdminCenter','ServerManagementGateway' |
  Select-Object -First 1

if ($null -eq $svc) {
    Write-Error 'No recognized Windows Admin Center gateway service was found.'
} else {
    Set-Service -Name $svc.Name -StartupType Automatic
    if ($svc.Status -ne 'Running') { Start-Service -Name $svc.Name }
    Get-Service -Name $svc.Name
}

The expected result is Status: Running. Next, test both endpoints locally on the gateway:

Test-NetConnection localhost -Port 8888
Test-NetConnection localhost -Port 6515

Open https://localhost:8888 locally. If that works but access from another computer does not, retain port 8888 and check the gateway’s Windows Firewall rule rather than reconfiguring WAC. Any inbound rule should be limited to trusted management networks; do not expose the port broadly.

3. Restore port 8888 only for a modernized gateway

Confirm that this module exists:

C:\Program Files\WindowsAdminCenter\PowerShellModules\
Microsoft.WindowsAdminCenter.Configuration.psm1

Its presence identifies the supported configuration mechanism for a modernized gateway. Microsoft documents Set-WACHttpsPort for changing both the public WAC HTTPS port and its service-port range.^3^

Before running it:

1. Determine the service-port range approved by your firewall/security policy or originally selected during installation.
2. Verify every proposed port is unused:

$start = <approved-range-start>
$end   = <approved-range-end>

$used = Get-NetTCPConnection -State Listen |
  Where-Object LocalPort -ge $start |
  Where-Object LocalPort -le $end

$used | Select-Object LocalAddress, LocalPort, OwningProcess

If no conflicts are reported, import the module, restore 8888, and restart the detected service:

Import-Module 'C:\Program Files\WindowsAdminCenter\PowerShellModules\Microsoft.WindowsAdminCenter.Configuration.psm1'

Set-WACHttpsPort -Wacport 8888 `
  -ServicePortRangeStart <approved-range-start> `
  -ServicePortRangeEnd <approved-range-end>

Restart-Service -Name $svc.Name

Do not invent a new service range or use this command on a legacy gateway.

4. If the splash screen still remains

• Review Event Viewer → Applications and Services Logs → Microsoft-ServerManagementExperience or the WindowsAdminCenter event channel. WAC writes gateway activity there for troubleshooting.^4^
• Try an Edge or Chrome private window. If it works, clear the normal browser session’s cache.
• Only if WAC is opened inside the Azure portal: allow third-party cookies. Microsoft specifically documents blocked third-party cookies as a cause of the WAC logo/loading page remaining displayed.^5^
• If the service is missing, will not remain running, or localhost cannot load either endpoint, uninstall WAC, reboot, and install the current release again, selecting port 8888 during setup. Reinstallation is Microsoft’s documented fallback when the gateway installation cannot open.^2^

References

1. What is Windows Admin Center?
2. Troubleshoot Windows Admin Center
3. Windows Admin Center frequently asked questions
4. Event logging in Windows Admin Center
5. Manage a Windows VM using Windows Admin Center in Azure