Looks good currently, maybe apache needed a restart? I see the sites aren't configured to auto redirect http to https but the https version of each site is working.
Thanks for looking into it! Much appreciated.
And indeed it now seems to work for me too. I DO religiously restart apache after messing with .conf files, so I wonder if this cert stuff is maybe cached somewhere, with a cache timeout? (Although these four were all done at the same time).
Oh well, not important: it works now.
Some more information!
It appears to be a Chrome browser issue! When I tried this 10 minutes ago in a new tab, to my surprise it indeed worked the way it should.
Then I noticed I still had a tab with the failed attempt, and I did a refresh, and again it said 'Site not secure" (but oddly, if I expanded that 'Not secure' message, it DID say 'certificate valid').
I then browsed to something else, from that tab, which worked, and then I typed in the failing https URL again and AGAIN it told me "Site is not secure". When I then removed that tab, and typed in the same URL in a new tab, it worked just fine.
So, it must be a Chrome issue, with not clearing things (cached?) on a per tab basis. Deleting those tabs fixed it.