Windows Plesk panel actions hang completely or are very slow: Error during WebSocket handshake

Symptoms

• Plesk GUI menus require a significant amount of time to load

• Attempts to install or update extensions via Plesk > Extensions always end up in a queued task which does not get executed anytime soon

• Browser DevTools (F12) shows errors such as the following under Console tab:

  Failed to load resource: the server responded with a status of 404 (Not Found)
  :8443/manifest.webmanifest?1607564336:1 Manifest: Line: 1, column: 1, Syntax error.
  WebSocket connection to 'wss://example.com:8443/ws' failed: Error during WebSocket handshake: Unexpected response code: 502

• The C:\Parallels\Plesk\admin\logs\php_error.log contains multiple errors such as the following:

  CONFIG_TEXT: [2025-08-20 17:52:56] 141428:68a5ef58168ce ERR [panel] Request to ws-server failed with response: 403 Forbidden

Cause

The PleskWebSocket service (ws-server) is either down completely or it is stuck in a state that does not allow it to function properly.

Resolution

1. Connect to the server via RDP

2. Go to Windows Start > Services > Plesk Web Socket Service > Right-click > Restart

3. If the issue persists, reinstall the PleskWebSocket and restart the service by using CMD commands below:

   plesk sbin nssmmng --reinstall-service --name=PleskWebSocket

   net start PleskWebSocket