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:

error-dialog-number-of-activations-exceeded-EZSuite


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...

Help-About-Deauthorize


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

help-deauthorize-computer

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