For each license code, the number of computers on which it may be activated is predefined.
Once this limit has been reached you may encounter the message: Number of allowed activations has been exceeded:


This may simply mean the license has been activated too many times. 
In this case you can simply deactivate your license on another machine by using Help/ About/ Deauthorize...


The license will then be free to use on a computer of your choosing.


Note that you do not need to uninstall when using this option.