The cause appears to be the use of non-ASCII characters in file names. Microsoft describes it like so: “Any user may be ...
There is a workaround, though.
Open-source tool that made Excel obsolete ...
Microsoft has started looking into a problem that is preventing users from opening some Excel file attachments with non-ASCII ...
A Model Context Protocol (MCP) server that lets you manipulate Excel files without needing Microsoft Excel installed. Create, read, write, and analyze Excel workbooks (.xlsx, .xlsm) with AI assistants ...