Enable Cross-Origin Resource Sharing (CORS) on your Acrolinx Platform. Check out this article on how to enable CORS.
Secure End-User Communication with Acrolinx
Make sure that you secure end-user communication with Acrolinx, because Acrolinx for Microsoft 365 Word only connects to Acrolinx using HTTPS. This means that your Acrolinx URL in the Sidebar has to start with the prefix
https and follow this pattern: