Are you invoking the picker by pressing the space bar, or holding it? Both should be valid and you can toggle that behavior in the Tool menu, but I've noticed some laptops lock out the trackpad when typing is happening (eg a key is being held). If you open a text editor and hold spacebar, does the trackpad work? If not it might be a hardware/OS level issue. Let me know if the behavior only happens with Playscii; it might be due to a quirk of SDL2 for example.