The thermometer I soldered doesn't work

Yesterday I bought a second soldering iron, as well as solder and rosin flux.

I spent two hours soldering all the parts onto the circuit board. The most time it took me to solder the connectors that are used for temperature sensors and power supply.

The set was high quality do it yourself, but required also a high level experience in soldering. Many parts needed to be soldered on both sides of circuit board. I thought it was enough to use much flux so than the solder would cover the metal legs of the parts on the both sides of the board. I was wrong.

Anyway, I had two hours of great time (I love doing such stuff), but in the end the termometer didn't work as it's supposed to. Something did work but also something didn't, as you can see on the photo below:

So I ordered another thermometer, electronic one as well, but this time a completed device, not a diy kit. ;)