Hi,
Yes, you are correct. I installed Windows 10 N. With the N version, Windows Media Player isn't installed. After I installed Windows 10 Pro, Sonicstage 4.3 works flawlessly! I didn't even had to install a driver for my Sony MD. After connecting my Sony through a USB a connection, my Sony MD showed up as a USB storage device.
I used this version of Sonicstage:
SS43_ULTIMATE.exe