If you use the delete node button, the tag editor for the OSM layer, or the OpenStreetMap Tags Editor extension, you may have started to see a popup with an invalid authorization.
This is a consequence of OSM OAuth authorizations are failing across multiple services due to popup windows
In this case, just open the iD editor.
I use the same authorization method as in OpenStreetMap Tags Editor, using the osm-auth library. If you opened iD, the library reuses the token from iD. Otherwise, it tries to authorize you and now it doesn’t work.
OAuth, dependencies. I love it </sarcasm> On replacing Basic Auth with OAuth 2.0 - #18 by TrickyFoxy