Not quite sure why this thread was “solved” and closed. Guess this was included in the recent house cleaning where a dozen or more active threads were arbitrarily closed.
I determined what was going on…
When I moved my site to DH some years ago, there was no HTTPS setting & no free certs. I coded this myself & installed my own cert. Later I saw that LetsEncrypt was added as a free install so I switched to that, but I was never aware that a setting for HTTPS had been added to the panel since I rarely look at my domain settings.
Upon inadvertently stumbling upon the HTTPS setting in the panel, I switched it on and tested. Then I removed my htaccess HTTPS 301 code and tested.
All is well