The symptoms were identical with previous episodes (four now, I think). I booted the pc up and it seemed to take longer than usual. I opened my browser – Firefox – to be told it was not the default browser (it opened, nevertheless, with no problem at all). I tried the start menu – fatal error.
I ran the fixes as before; now the start menu still does not work although no fatal error when I try to enable it, but the system refuses to recognize Firefox as a browser and Microsoft Cloud has disappeared.
After Easter, I propose to telephone Microsoft and demand a fix. More than six months after the ‘upgrade’ and the system still fails; not in some minor, esoteric detail, but in the basic function that allows access to the system. I really do not know how those buggers get away with it.