RealBand on my Windows 10 machine is the only DAW that struggles to find the MIDI input. I see this problem dating back to 2009 in the forums and both my RealBand 2016 and 2021 behave this way!

This is the sequence I use to make it work:

1. While in RealBand, set up your audio, I use ASIO Drivers on a FocusRite USB Scarlett interface
2. Goto Menu -> Options -> Reset to default settings. Press Yes in dialog to reboot the program with factory settings
3. Now you will get the infamous The Input Device 'usb midi' is not installed on your system. Just press OK
4. Now you can get dialogs for:
a) Midi Driver Setup to pick input and output
b) Select Folders for files just tick the Don't show this dialog again and press OK
C) ASIO Audio Drivers just pick your interface.
5. If you did not get a dialog for ASIO Audio Drivers, make sure your audio is set up right again; the program tends to change things
6. Now on my machine, each time I run the program, I have to go through the dialogs for ASIO Driver Setup and MIDI Driver Setup
7. Use your MIDI monitor to check for input
8. Don't even think about changing MIDI now from the MIDI Devices icon!
9. If you screwed up, try the Reset to default settings again and start over, try different combos if needed

Hope this helps. Keep practicing . . .