Hi just want to share something I found when I couldn't get Prey to run at one point.
If you have encountered issues that your Prey somehow couldn't find your device when when it is already installed on your PC, single boot or otherwise (and regardless of which OS you were using to try to use the Prey panel), another possible thing to check: check to see if your motherboard BIOS settings has secure boot disabled.
You will need to enable it again to make Prey work. However, some of you may need the config disabled for your Linux based OS.
When I encountered such issue back then, I thought it was a newer version of prey that didn't work on my Ubuntu because I just updated it, and the last time it worked was before update. I also happened to need secure boot disabled again for an update on something else.