serial number is already in use

Please go to Adobe Customer Service and only ask to have your activations reset (Make sure to sign in to your Adobe account first and allow popups and cookies on your browser. You may not be able to see the chat window if using a VPN.):
https://helpx.adobe.com/contact.html?rghtup=autoOpen will automatically open the chat window.
Type "Agent" in the chat box to bypass the chatbot and be connected to a person.

You may also be able to contact Adobe by phone:
https://helpx.adobe.com/contact/phone.html

or Twitter:
https://twitter.com/AdobeCare

Can you give us a screenshot of the message you are receiving.

Since you have had a number of computers on which Elements 13 was installed, it is likely that you have exceeded the activations somewhere along the line, even if you think you have deactivated them.  As @Test Screen Name suggests, it is not sufficient to uninstall the program on the other computers.  You have to sign out from the Help menu. 

Since this is a user-to-user forum, there is absolutely nothing we can do to help you with activations.  That requires you to contact Adobe support.  (It doesn't take very long. So perhaps you can do it on a lunch break.)

Otherwise, if you have only uninstalled without signing out on the other computers, I suggest you try to install again on the other computers and formally sign out from the Help menu.

There is no email address. (Don't believe anyone who tries to tell you that there is - they will be trying to rob you).

How did you deactivate exactly? (For example, did you just uninstall?)

also i cannot ring customer support as they are only open during office hours and I am at work during them times but cannot find an email supprot address