SharePoint.Files "Token refresh timed out" since late May 2026 - fix inside

Hi Henri- 

That is an incredibly sharp diagnostic catch, and thank you so much for documenting this workaround for the community! That background change by Microsoft regarding legacy authentication protocols has been causing silent token drops across a lot of tenant configurations lately. To add some extra technical weight to your explanation for anyone trying to understand why this happens: when Enable fast data load is active, Excel prioritizes raw ingestion speed by pulling data on a separate, heavily optimized thread that skips the standard user-facing authentication handshakes to save memory. Because that secondary thread operates in an isolated background container, it is completely blind to interactive OAuth2 renewal prompts; the moment the initial session token expires or requires a routine refresh mid-stream, the process instantly times out with a permission failure. Disabling fast data load forces Excel to synchronize the data pull directly inside the main application thread, allowing the underlying Power Query engine to leverage your live, foreground Windows session to seamlessly rotate and refresh the SharePoint OAuth2 tokens exactly like it does when you are working inside the Power Query Editor.