Enable Cross-Origin Resource Sharing (CORS) on your Acrolinx Platform. Check out this article on how to enable CORS.
Acrolinx browser Integrations only connect to an Acrolinx URL with HTTPS. This means that your Acrolinx URL in the Sidebar has to start with the prefix https.
Make sure that your HTTPS certificate is trusted by your browser. Otherwise, when you try to access your Acrolinx URL you'll see an error that "Your connection is not private."
Older Acrolinx versions might need extra help recognizing some HTTPS files. To configure this, you can use the property
10000.HTML = https?://.*.
See Configure Acrolinx to Recognize Your File Type to get started.