Just did that (re-install) that and updated the config file with my information. Running /usr/share/prey/prey.sh --check gave back the same "no laptop-detected in..." and 422 status messages like previously.

I wonder if it has to do something with my new Prey account. I set it up just yesterday (didn't have one previously).

On Prey Help Center someone with status responce 422 connection error got following answer: "Now, the reason why Prey is having trouble registering your device is because it’s trying to call a function that, for some reason, hasn’t been loaded (full_hardware_params). "

Unfortunately I can't do anything with that answer

EDIT: I'll try it out on another Sailfish device. Let's see what happens there.
EDIT2: Ok, tested it with another Sailfish device (fresh install) and got the same problem.