Activation issue-Adobe-CS6 Design & Web premium on Server 2016

CS6 authenticates using the IE component.
However, since IE is no longer supported, that authentication method is no longer available.
A simple solution would be to install the Creative Cloud desktop application.

However, it is not originally guaranteed to work on a server OS.
Windows XP/7/8 were supported, and those OS themselves are no longer supported by Microsoft.

Of course, the only thing you can do when you put it in a server OS is normal face-to-face operation.

you're better off using off-line activation: disconnect from the internet and restart activation. then opt for offline activation.  note your request code and leave that panel open on your older computer.

use an up-to-date computer or mobile device to connect to adobe where you'll be prompted for your serial number and request code.  enter both and you'll receive a response code which you enter into the older computer panel that had your request code.

Update your system & browser to support TLS 1.2 protocol.  You can't connect to Adobe's activation servers without it.

Check this site and report back if it does not solve your problem: https://helpx.adobe.com/x-productkb/policy-pricing/activation-network-issues.html

Well, indeed, support has ended. Many years ago. No corporate server should be running unpatched software. The current version is the subscription-only Creative Cloud. However the system requirements are now for Windows 10 only, so I don't think you can install to your server.