Excel Copilot fails when local workbook filename contains #

Kidd_Ip, your breakdown is spot-on and incredibly practical. I particularly appreciate how clearly you distinguished the local workaround (renaming) from the officially supported cloud workflow (OneDrive/SharePoint). That was exactly the nuance I needed to reinforce in my original reply. Your suggestion to adopt a file-naming policy that avoids reserved characters is simple yet brilliant – it’s a proactive habit that will save teams from running into this and similar issues down the line.

Patrick2788, thank you for that fascinating historical context! Knowing that # caused headaches back in the SkyDrive days makes so much sense now. It really highlights that this isn't a brand-new quirk, but rather a long-standing parsing behavior deeply tied to how Microsoft handles URIs and file paths. Your insight perfectly explains why this bug keeps resurfacing and adds even more weight to Kidd Ip policy recommendation – if it's been problematic for over a decade, avoiding it entirely is clearly the safest bet.

Together, you’ve given the definitive answer for anyone facing this issue: rename locally, store in the cloud for full support, and adopt a safe naming convention going forward.

Thanks again for taking the time to share your expertise – this thread is much richer and more useful because of both of you!