This is only for Reallusion old products, such as iClone 4, CrazyTalk 6, FaceFilter Studio 2, popVideo or earlier version.
To protect your copy against piracy every serial number has a five time installation limit. Please note that this limitation is by no means absolute. If you have to install more than five times just notify us with your purchase data + serial number and we'll reset the limitation. This measure ensures that honest users like yourself can be certain that others will not get for free what you have paid for.

Furthermore, we generally recommend to do a proper uninstallation of our software while your computer is connected to the internet. In the same manner that the setup connects to our server to validate your serial number during the installation procedure, the setup will also connect to our server during the uninstallation procedure to notify us. This way the five time limitation will not be reached.

Whereas for new Reallusion products, please refer to below FAQ to deactivate your product if you've exceeded the installed number of the purchased seats: -

https://kb.reallusion.com/General/50059/How-to-correct-license-is-exceeded-the-installed-number-message