Enable Cross-Origin Resource Sharing (CORS) on your Acrolinx Platform. Check out this article on how to enable CORS.
If you protect your content with Microsoft Purview Information Protection (MIP) sensitivity labels, you can exclude labeled content from your Acrolinx checks. To set this up, send a list of your organization's accepted sensitivity labels to Acrolinx Support.
Secure End-User Communication with Acrolinx
Make sure that you secure end-user communication with Acrolinx.Acrolinx for Microsoft Office 365 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:
https://<SERVER_ADDRESS>:<PORT>