It is always easiest to just uninstall from an old computer first (while online), however if you are not able to uninstall because of hardware issues, you can manually deactivate.

Please follow the steps below to deactivate your license from a computer. 

1. Login here: https://www.reallusion.com/member/#/en/registration

3. Click the "Details" link in the Activated Number column.

4. Scroll down to see the computers currently activated.

5. Click the "Deactivate Now" link to remove a computer.

6. You will now be able to install again on a different computer.

I hope this helps.