If you are using Windows 10 there seems to be a Microsoft bug introduced with the 2018-10 Windows updates, see here.

]]>https://community.notepad-plus-plus.org/topic/16580/faq-can-t-set-notepad-as-a-default-program-for-any-extension-windows-10RSS for NodeSat, 08 Aug 2026 19:12:48 GMTTue, 06 Nov 2018 14:14:08 GMT60