[May apply to more than Linux]: the 'add device' option on the website gives only an installer

I had Prey installed already - I’d copied the .deb from another computer and used that .deb. But once Prey is installed, it does not show up on the website. (Now admittedly my other Linux computer often doesn’t report its location - but that’s another problem. The current problem is that not even the device name of the new device appears on the website. Where indeed do I give it that name? Why doesn’t the site’s ‘add device’ say something about this?

EDIT: OK, I’d copied prey’s configuation from my old computer too. Removing that (via sudo apt purge) and reinstalling prey . . changed nothing.