Kmail not reflecting contents of ~/mail (maildir)

The problem is although my (maildir) ~/mail database contains an 
.inbox.directory of around 20 sub-folders, Kmail now fails to show ANY of 
them, even shows an empty Sent folder, and fails to show any Inbox emails 
older than the date after which I became aware of the problem, and now 
fails to download any emails.

  N.B. I have temporarily migrated to Thunderbird for email purposes.

Presumably there is an Akonadi/Baloo mixup somewhere, and I ask if anyone 
can here vrecommend a way of achieving re-indexing of the files in ~/
mail, 
please.

[I don't think it's a Kmail problem, as with another user on the system 
it is behaving normally.)

-- 
/\/\aurice 
	(Retired in Surrey, UK)     Registered Linux User #487649
		      Linux 64-bit Mageia-6:    KDE Plasma 5.12.2
      Virtualbox 5.2.14   Firefox 52.9.0  Kmail 5.7.2
           Thunderbird 52.9.1   Pan 0.140