Connect 2 monitors to a laptop, no picture is displayed on one monitor?

I had to buy a Lenovo brand docking station because of my job. I have 2 Lenovo monitors (D27-30). I have an HDMI connector for both monitors. I was able to connect one monitor to the docking station without any problems (where the only HDMI point is). For the second monitor I bought an adapter where I plug the end of the HDMI connector into the adapter and the end piece (DisplayPort) into the docking station. Unfortunately, the monitor that was connected with the adapter is not recognized. I have already restarted my laptop several times and also removed the plugs and reconnected them. Do you have any tips on what else I could try? Do you know why it doesn't work?

There's a category Display in the system settings. Look there, there's the option to duplicate or extend the screen

There you will also find all connected devices to see whether they are really not recognized

I did that, only one monitor is shown to me. The second is not recognized at all.

HDMI is not directly compatible with Displayport - the reason that you can usually connect an HDMI monitor to a display port via an adapter cable is for the following reason.

The DisplayPort recognizes when an HDMI monitor is connected and then switches to HDMI.

This detection may not work for you - but can't tell you why.

I would leave out the intermediate piece and buy a high-quality cable that has HDMI on one side and DisplayPort on the other.

I would also check for updates for Windows and install the latest drivers for your graphics card and docking station.

Thank you for your help. I only find cables on Amazon that convert from DisplayPort to HDMI. Can I also use this? If not, could you maybe send me a link from the correct cable?

From DisplayPort on the dock to HDMI to the monitor should theoretically work. Not the other way around.
Does the monitor work when you connect the HDMI cable from the other monitor there?
If so, then at least this interface has nothing.

On the monitor where that doesn't work, HDMI is already selected as input, right? Everything well and firmly plugged in, probably too?
Have you already tried to simply swap the monitors, which one you connect and how? Vlt works with the other with the adapter.

The DisplayPort interface on the dock shouldn't have anything after it's new, but who knows. The dock will probably have a second DisplayPort interface. That won't work either?

Well otherwise you can try another cable as someone said. So a single cable which has a male DislayPort and a male HDMI connection. So no adapter plug… Although that shouldn't be a big problem in normal cases.
Otherwise the monitor will probably also have other connections. In the ideal case DisplayPort, then it is obvious that a pure DisplayPort cable is best for this.
Otherwise it will probably have a DVI and / or VGA connection. If a DVI connector is available, you can also buy a single cable with a male DisplayPort and a male DVI connector. Should go in that direction too.

In extreme cases, the monitor is too stupid for certain adapters because it is too old.
I already had it with a customer.
So if that is the case, it may be that DP works on DVI, but DP on HDMI doesn't… Whatever the case… 😄
It's just annoying when you have to buy extra cables without having a 100% certainty that it will work.