@AnitaM9908 dang if this was a CC Adobe app, then you could use the option to deactivate your apps from the account management page BUT this is only supported for Creative Cloud desktop apps. I had to look online at Adobe Acrobat XI Pro was released on October 15, 2012. And according to Adobe's Help Center, support for this version officially ended on October 15, 2017. And because of that, the activation servers for older versions like Acrobat XI Pro have been retired, you likely won't be able to activate it on your new computer through the standard online method. Since you can't deactivate it from the old, failed computer and it's not showing in your account, you're in a difficult situation.
I am assuming you are on a PC, and there are some users who have reported success running older software in compatibility mode on newer operating systems like Windows 11, it's not officially supported, and you might encounter issues with stability, functionality and security (that's the main one for me). Given that support has ended, Adobe can NO longer provides updates or addresses compatibility problems for Acrobat XI Pro. Your best course of action would likely be to consider upgrading to a newer, supported version of Adobe Acrobat or exploring alternative PDF software that is compatible with your current operating system.
You could try customer support as this is a community of users and isn't all the time monitored by Adobe Customer Service