Adobe Acrobat 11 Pro : cant register

Im having the same issue

Acrobat XI is an old and unsupported version, and is no longer compatible with any current OS, so problems are to be expected. To increase the chances of it working properly make sure you have all updates installed (up to 11.0.23) and run it in Compatibility Mode with an earlier OS, like Windows 7.

Updates are available here:
ftp://ftp.adobe.com/pub/adobe/acrobat/win/11.x/
You must use a dedicated FTP client to open the link, it won't work in most browsers.