Heatermeter 4.3 Building problems

Hello,

I built the heatermeter 4.3. yesterday, but I have a little (or big), problem.
The display led turns on but I can't see anything on the screen. I already checked the potentiometer, and its works well.
The heatermeter boots well, because I can access via web browser, and detect the probes. I tried test the alarm, in the alarm settings (pushed the test icon) , but this does not work. What could be the problem? Maybe I burned out some components when I soldered in. I attached a couple picture for you, I hope you can help me What should I test and how? (I have a multimeter, but I'm rookie)

Photos


Thanks for you effort and any advice!

Gabor

I found the problem, It was a potentiometer. (Poor soldering ..)

But the speaker problem is not solved yet . I can hear, but very quiet.

My speaker is also not beeping but everything else is working great.