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How-to fix error 500 - ALIS Web not loading properly

A blocked connection ( error 500 ) can be caused by:

  • No internet connection

  • AdBlocker / Cookie blocker browser extensions

  • Antivirus and Firewall software

  • Proxy and VPN connections

To make ALIS  work properly, it's important that the connection between your web browser and ALIS is not blocked. These are the so-called Websocket connections.

Websockets are connections that allow us to process live changes in ALIS, without you having to refresh your browser. This is used to make any changes by your colleagues directly visible on your screen.  Without WebSocket connections, unexpected errors may occur while you're using ALIS .


  1. First, try using ALIS with Google Chrome, instead of another browser.

  2. If you are already working in Chrome, try the Guest mode in Google Chrome.

If the error does not appear anymore after these steps, the cause is probably a browser extension that is blocking websockets. Do the following:

  1. Disable your browser extensions one by one and try ALIS again. This way, you will find out which extension may be causing the issue.

  2. In some extensions, you can configure what domains to block or allow. Remove or add the following domain to that extension: 


If you still get the error in the Guest mode of your browser, your antivirus or Firewall may be the cause.

  1. Temporarily turn off all antivirus or Firewall software, or try a device without this software (for example an iPad).

  2. If the error stays away, your antivirus or Firewall is probably the cause.

  3. At this moment, we can't determine which specific antivirus or Firewall software is blocking the websocket connections, or how to prevent this from happening. Please ask your IT manager to allow websockets via wss://

If you still get the error, it may be caused by proxy or VPN connections.

  1. Please ask your IT manager to allow websockets via

JavaScript errors detected

Please note, these errors can depend on your browser setup.

If this problem persists, please contact our support.