Strange behaviour K8064

I have built the K8064 dimmer, and it seems to work just fine after adjusting the 2 potentiometers. I then disconnected everything to built the thing into it’s box. After that I reconnect everything, but I couldn’t get the lightbulb to light up. Measuring the output (with the lightbulb connected), always gives me 0V, no matter what the input value is (0-10V). The output always measures 230V with no load attached. After re-adjusting the two potentiometers, everything works again. This happens everytime I disconnect the source it seems. Any ideas on this?

Does the LED give any error condition ?

Thanks for that hint; I should have thought about that myself! It gave error 4 (no load). Seems that there has to be a load connected before adjusting the input value. When I keep that in mind, it works perfectly. Thanks again!