Hi @David-Lucas Assuming you have a Magix version of Sound Forge (12-14), you can activate and use SF simultaneously on two (2) PCs.
If you need to activate SF on third or different PC, one of current activations will need to be deactivated.
FYI, there are two ways to do this - Visit the MAGIX Service Center, log into your account, go to "My Products > Show More Details in the product list > Deactivate". This option can be used only once a month. - The alternate option is: Go to the SF 'Help' menu choose "Deactivate this Software on this PC". This option can be used as often as you wish. The PC needs to be connected to the internet. Note: the 365 subscription version can only be activated on one device.