One single license can only be installed on two machines that can be used one machine at a time. It seems that you already installed and activated Adobe Presenter on two machines. In order to use it on the third one you will need to deactivate Adobe Presenter on any of the machine and then activate it on the third one. To deactivate Go to : Presenter >Help > Sign-out/deactivate.
In case you still face any issues please send me a private message with your email ID and I will contact you back and assist. Alternatively you can also initiate Chat online and get help from support and surely they will fix for you. To initiate Chat click on the following link : Chat with an Expert