Using classic Outlook for Windows in business environments
Sadly, /cleanviews had no impact whatsoever, which seems rather odd baring in mind that that would seem to be its role in life.
However, your suggestions did start me on a route to a solution.
Firstly, whilst I couldn't see the "Reset View" button, I realised I could add it to the Quick Access bar which was visible. Sadly, it was greyed out.
However, I then looked at one of the other Calendars which was displaying OK, and went to View > Change View > Apply Current View to Other Calendar Folders.
And that worked perfectly. I only wish I knew how I got into this mess! I did not knowingly make that change, but must have done it somehow, in resetting my Calendars. I was fiddling about trying to hide the Birthdays Calendar as I have not been able to turn it off despite doing so in Outlook.com, and I probably changed something in error.
Many many thanks for your help. I really appreciate it. Volunteers in Community Groups give up so much to help, and I for one am very grateful.
Colin