BenQ screen shows blue picture? HDMI connection?

Yesterday I dug out an old BenQ monitor from my basement (BenQ G2400W LCD monitor). I would like to use it again, but when I turn it on, only a blue picture appears. However, this picture only comes with the HDMI connection. Both when there's no HDMI cable in the monitor and when an HDMI cable is connected. Nothing changes when I connect the cable. The PC / laptop does not recognize this either.

With the two other inputs D-SUB and DVI D, the screen only says it can't find a signal in a black window. I haven't tried these connections yet because I don't have the right cables.

I also opened the screen to see if the HDMI socket was still in place and had no open solder joints. Everything still looked completely from what I could see under the microscope.

My question now, do you know why that could be or how I can get it to work again via HDMI. Where could the fault lie and can it be repaired?

After your stories I come to the conclusion:

The monitor is still OK in the image system. → Proof by the function of the other sockets.
However, if you switch to the HDMI port without connecting a cable, it will turn blue. → What else do you need as a reference?

You already looked right. Tell me that you got the same result. The error is likely to be on the route from the HDMI connection to the IC on which the different video standards are merged.

Or in other words: the monitor is defective.
My tip: Compare the price of the monitor with the repair costs and then decide.

First, thanks for the answer.

I thought maybe something is wrong in the settings on the monitor or the error can be fixed in some other way. But think that for me, as an ignorant person in the field, this does not allow much to be done.

I have now ordered a DVI - HDMI cable and tried it, but here too he tells me that there's no signal, no connection. (no hay cable conectado). I have no idea why that is in Spanish.

So I assume that the screen generally has a problem with the transmission of the image.

I had let the past guide my answer too much. In the case of an analog system, one could assume that a short circuit has occurred in the connector. But HDMI is a digital system. The fault here is an interruption in the signal and thus the absence of the image signal. So one color would be missing from the color lines. With the others, the transmission fails completely in the worst case. A color error like yours then rather indicates an error in the IC. They would swap the entire circuit board for you. Depending on the size of the television, the repair costs are almost the same as buying a new one. Repairs should only be worthwhile for the very large devices.