When I try to install some add-on in Blender 2.91 via the usual method, Blender immediately confirms that it loaded the add-on successfully via the blue tag that appears at the bottom of the screen.
The un-zipped add-on also appears in
Yet, it may take a few minutes until I see the activate tick box, if I see it at all. Windows 10 Pro and all software drivers are up to date. I’ve uninstalled then reinstalled Blender 2.91 several times. No error message appears.