Experimental 1788 Vehicle Tracking Devices don't work

Tried de/reactivating, installing/uninstalling, tried activating the PDA in my inventory, tried activating a control laptop in case the required tool had changed, and pretty much anything I could think of, and the c still doesn’t appear where it should on the map.

Same here. Ver 1832. Removed and replaced the device, did the stupid human PDA tricks.
Maybe I should make a zlave, strap him to the roof and apply regular electric shocks so I can home in on by the groaning.