I don’t believe in fish. They‘re just actors hired by the government. Wake up, sheeple!

Checkmate!

I just posted the update as an edit of this post.

Thank you again for the help and the links, that was really helpful while troubleshooting!

Thank you for your quick response!

Did you test your equipment before soldering it together? Then after soldering it does not work?

Unfortunately I did not, but the arduino and the power supply were already in use as an ambilight some months ago (I bought a preassembled kit back then). I got a new screen, so i stored the devices until yesterday, when my new LED strips arrived. Everything worked until then.

Is it three wires you are connecting: 5V power, +data (PD5), then ground connection on the strip?

Exactly. Also for good measure I also connected ground from the arduino with the ground pin from the strip. Is that a problem? It used to be wired that way before… but the old strips had less LEDs.

By this you mean that no V is seen or it is acting like it is not connected, it is binary so it has the neccasary V or it does not (0V or 5V).

I updated the fastled library on the arduino und set it to use port5 of the arduino. When everything is connected I turn on prismatik and it says it sends signals to the arduino. The work indicating led on the arduino blinks accordingly. But the led strip blink does not change. Unfortunately I have no device to measure if there is any output from the pad.

You need to make sure you did not fry the arduino. Is there a way to check it by software? But it behaves as it used to, when the old ambilight was working.

Quick search I found this short video with great information:

Thank you for the recommendations! I‘ll check them out!