PNP water level detector circuit
Problem: Learning curve error with Falstad drawing.
You had Red Dot below LED indicating it was not a junction (disconnected) So shink line and add another wire as in my comment link fixed.
But you had 12V with a pretty big LED current which only uses a couple volts which is very inefficient. So I assumed 20mA here.
Also remember to reduce hFE to 10% of maximum when using a switch.