You need to enable CORS on your server and then restart the server.
Your server administrator can sign in to the Dashboard, navigate to: Maintenance > Configuration Properties, open the file tree to server/bin/, select the coreserver.properties file and click Edit:
You can use a wildcard:
Or if you'd like to lock it down for only the Chrome extension you can enter specific details.
For example, in Chrome's options menu, go to More Tools > Extensions, then tick the "Developer mode" box at the top and make note of the ID of the extension:
You then need to add the following (as you can see above in our example, the ID is ocmlcpnpkbohcmjkjpdedobcaigojcod
After you've done this, save and navigate to the Servers menu and click Restart All Servers. Once the servers have restarted and finished initializing, the Acrolinx Chrome extension will be able to connect to your Acrolinx server.