How to re-activate or reinstall-then-activate CS6 in 2023 on Windows 10

I repaired an old computer of mine with CS6 installed there. OS is windows 10.

Now even I open a pdf file, the Acrobat will prompt for activation. 

I found my serial number in an old activation email from Adobe, entered it, but cannot get it activated.

I emailed customer support, they say the activation server for CS6 is retired.

I haven't tried reinstall-then-active, but given the server is gone, it shouldn't work.

I think I have the right to use the product permanently and should not be disrupted by some required reactivation depending on a retired activation server.

Anyone in the same situation or know solution for this?

Kind regards,

Joseph