[chsims1]

The problem is that I have tried all the suggestions, as I thought that I had made clear above.  I had stopped returning to the forum, because there were no replies.  There is a possibility that I have not been as careful as I thought to totally remove all traces of the previous software before trying another version.  I will try again, since people seem to be pretty convinced that it is a result of software and board manager versions.

I apologise if I have sounded frustrated, but that is because I have indeed been so.  Anyhow one last attempt with the Windows version of the IDE (1.8.8) & boards manager 1.6.21. I really want this to work.

Regards,

Ian