He had to move from one computer to a new CS6

I did uninstall my old computer, but when I go to install on the new computer it tells me that the serial number is already in use

Uninstalling is not really necessary, unless you need the space.  What counts is disable.  At this point, it seems that you should contact the Adobe Support via chat and ask them to reset your counter to activate.

To the link below, click on the still need help? the option in the blue box below and choose the option to chat...
Make sure that you are logged on the Adobe site, having cookies enabled, clearing your cookie cache.  If it fails to connect, try to use another browser.

Serial number and activation support (non - CC) chat
https://helpx.Adobe.com/contact.html?step=PHSP-PHXS_downloading-installing-setting-up_lice nsing-activation_stillN

Tags: Adobe

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