On those test points you are measuring the LDR’s resistance with the LED on, so if you have no reading it could mean that the LED is not on, which would make the LDR’s resistance very high (practically open). So make sure your LED is actually on. Measure the voltage across it with the depth knob fully counter clockwise (it should have around 1.8v dropped across it…compare it to the LOW side LED). Make sure it’s installed correctly. (When it’s off) Use your multimeter diode checker to test if it has the same reading as the LOW side led (make sure you measure both LEDs the same way…red on square pad, black on the round pad). Make sure all the solder joints are solid and there are no opens or shorts anywhere in that circuit.
Let me know what you find.
-Brach