I have a license to Design and Web Prem that I bought back in 2013. My activation limit has been reached, but I cannot see/deactivate old computers. How can I resolve this?

Right. Legacy CS apps can’t be remotely deactivated. That only works with currently supported products like Creative Cloud.  

Since CS is no longer supported, the best advice I have is to leave CS on your old computer. Use it until it works no more. 

Get supported software for your new computer. 

Photography Plan or 

Creative Cloud Pro

https://www.adobe.com/creativecloud/plans.html

System Requirements:

https://helpx.adobe.com/download-install/apps/system-requirements/creative-cloud-requirements.html

Hope that helps.

​@tjohnsonidaho 

adobe’s servers can record deactivations, but require your computer to meet adobe’s security requirements.  https://community.adobe.com/t5/download-install-discussions/activation-limit-reached-for-non-subscription-adobe-desktop-applications/td-p/14804413?linkId=100000305463075

See here:

In short: you can’t. The support for that version (CS6?) reached its end of life years ago. While the activation servers still exist, they are not maintained anymore, and deactivations cannot be performed.