Microsoft has confirmed a copy-and-paste issue affecting Excel 2024, 2021, 2019, and 2016 after the KB5002914 security update ...
German]The Microsoft security updates released for Office applications on September 8, 2026, are causing serious collateral damage. In Excel, it is no longer possible to select and copy anything.
You can fix Windows 11's copy paste not working by running an SFC scan or clearing clipboard data as outlined in this guide.