The error indicates that you have already activated this membership on two machines and you are attempting to activate it on a third. Deactivate one of the previous machines before proceeding. If you have access to the previously activated machines, choose Help > Deactivate within the application. Alternatively, you can deactivate all previous machines by following the steps below.
1) Launch the Adobe product.
2) At the Maximum Activations Exceeded screen, click Continue.
3) On the Sign In Required screen, click Sign
4) Enter your Adobe ID associated with your membership and click Sign In.
If the problem still persist, then please contact our Chat support - http://www.adobe.com/support/download-install/supportinfo/
It might be an outage, although a selective one. I got a guy that solved this by login out and in again, in the adobe Creative Cloud desktop app: http://helpx.adobe.com/x-productkb/policy-pricing/activation-deactivation-products.html
I have signed out on desktop app and still not working. It gives me the option to desactivate all other machines but still saying same message after relogging in.