So I just sat down and tried Troubleshoot via Activation and not the Troubleshoot button yesterday, and yes! I got a blue pop up thing instantly saying Windows is now Activated, or similar. (That one wouldn't screenshot.)
I thought it will take a couple of days anyway, and I haven't been on my pc much.
Windows would work up to now, and a manual check would show my Windows Updates were - em - up to date, though no Defender updates until I was re-activated.
There was a permanent screen reminder overlay in the bottom right saying not Activated.
This is today's before and after shots if it helps anyone (I'm sure it doesn't but I get a kick out of posting screenshots).
It seems I have a digital license linked to my MS account, as it was a free upgrade from W7 (pro), so no key. I will try those two suggestions anyway, soon (I'm in a hotel).
Thanks you guys for the help. :)


