Hi there,
Based on the screenshot and your description, it sounds like the issue could be related to permissions.
If your Copilot agent is running under a different identity (like a service principal or a user without access), it won't be able to read any of the documents in the SharePoint library—even if they appear fine to you. In the image, all documents were modified by a specific user ("Juan Pinillos"), so it's worth double-checking if the Copilot agent has access to those files.
Try sharing just one document with the Copilot identity directly and test again. If it works, then it’s definitely a permission issue at the library level.
Let us know what you find!