Recently released security update (for June 2026) seems to break the “Show sync folders in Explorer’s navigation pane”.
The menu position is there, but it doesn’t expand; checking the properties shows a broken element - like the GUID has been detached from the element and leads nowhere (0B size, 0B size on disk, other properties are empty).
I’ve compared the registry entries for Nextcloud before & after patch has been applied and there’s no difference (also did client reinstall, registry purge and ton of other stuff), so clearly M$ has broken something, because the update is the only common denominator.
The main difference is that trying to run ’ explorer.exe “shell:::{GUID}” ’ on the pre-patch machine opens main Nextcloud directory, where post-patch nothing happens, what confirms that there’s something off with GUIDs (parsing or anything else).
I have no idea whether they will fix it (or if they even know they’ve broken something) or maybe you’ll be able to get around that (I know it’s not supposed to be like that, but you know how it is nowadays).
Either way, just dropping the info for anyone that will bump into that and will wonder what the heck has happened.