. . . . Are there specific USB MIDI drivers for WIN 11 . . . .
Try restarting the computer to see if the keyboard appears - Windows button, Power icon, Restart - not a Shutdown and Start
Assuming you cannot select the keyboard in Music Maker, in theory the generic Windows 11 drivers should have been installed, however check with the keyboard manufacturer to see if they have Win 11 drivers - if you can only get Win 10 drivers or have them already try re-installing them.
Thx John. Nothing seems to work. The (cheap) keyboard is a Medeli MC49A and they don't have any MIDI drivers available. The only thing I do not understand why it isn't working any longer is that the drivers of a WIN10 and a WIN11 should be the same. But unfortunately no-one can give me an appropriate answer
@Paul-Ranft Is your keyboard listed in the Windows device manager? It should be listed under Sound Video and Game controllers (you can also see hidden devices under the View menu in case you cannot see it). You might try to uninstall it via the right click menu, unplug it, then restart your computer and connect it again. The driver should automatically install itself.
If it's listed as an unknown USB device In the device manager the drivers aren't working.
Make also sure you use the original USB cables or USB cables that aren't too long or else you can get connection problems.
The keyboard is not listed in Device Manager. I checked with 2 different usb-cables that both work fine with my printer and also worked fine under WIN10 (with the keyboard)
It seems that the MIDIside on the keyboard itself is not okay. But that is hard for me to belief. Unfortunately I only have one PC. Otherwise I could check it.