Syncing problems - iTunes to iPhone SE

My music files are downloaded to my Windows 10 desktop PC on which iTunes is installed (running Version 12.13).  I then sync iTunes with my iPhone so the full library is then on my phone .  Until recently this was problem-free.  However, iTunes has recently stopped recognising my iPhone [iPhone SE, 2nd generation]. My wife's slightly newer iPhone SE 3rd generation is not recognised by iTunes either.  However, iTunes DOES recognise my iPad mini 4 which is two years OLDER than my iPhone.

I ran iTunes/Help/Run Diagnostics/Device sync tests with iPhone connected to my desktop by USB: the result, was “No iPod, iPhone or iPad found”.  However, this is clearly NOT a

“connection” problem as an identical test for my iPad mini ran successfully.

Has something been changed by recent iTunes updates to cause this problem?  And how can I resolve this issue