Update
I installed the previous version 10 from an archive I had kept only to find it would not activate. I contacted DXO support who advised they unable to activate older software. What a waste of money. Beware if you want to reinstall older DXO products on a new PC!
I'm of two minds on this. On one hand, I don't expect support forever. PhotoLab 10 was the current product from Oct 30, 2014 (
DPR article) until June 1, 2016 (
another DPR article), so depending on when purchased, it's somewhere between 6.9 and 8.5 years old--and you got it for free, right?
On the other hand, rather than blocking activation of older software, which in many cases was lawfully purchased / licensed, it seems reasonable that, if they can't bother to maintain the activation server, then they should either give all licensees reasonable notice (like email everyone on the list) and a reasonable time period (a few months) to download an 'unlocked' version, or else they should program their servers to simply grant all requests to activate the too-old software.
But my opinions and musings won't get you far. I'd take this up on the DxO support forums (
https://feedback.dxo.com/).