Laptop brightness can't be adjusted?

I'm having a problem with my Lenovo Ideapad 530s. I had to do a little maintenance on the device and open it up for it. After a successful operation, I have the problem that the brightness of the display can only be set between very dark (i.e. Barely noticeable shimmer) and maximum. Could I have caused something and can I fix it? I have already tried to fix software-related problems. The picture shows the laptop open (only the model without a dedicated graphics card, but identical in construction.

I suspect that this has nothing to do with the inside of the laptop but rather the driver or a Windows error.

My recommendation is:

Contact Lenovo Support, they know exactly what is going on.