I think Windows made another change and you now have to go into Windows Settings> Apps> Default apps and select MusicBee as your default Music player for the Explorer Menus to stick.
I went to Windows Settings> Apps> Default apps. I reset all to Windows Default which made Windows Media Player the default for Music Player. I then selected MusicBee for the new default and now the Context Menu items for MB REPLACED the Windows Media ones.
Success? Yes.... and no.
The above was for the Portable version, so I figured I would now try again for the Desktop Version. I removed the Portable version, reinstalled the Desktop version. However, when I went into Windows Settings> Apps> Default apps, the drop-down only allows me to select the Store version app, with no recourse to choose the Desktop version/exe, nor even after I manually chose a few file type associations.
Ok, so I uninstall the Desktop version, install the Store version, and then select the Store version as the default.... MB Context Menu items won't show in Explorer.
Now I am back to using the Portable version. To get the MB Context Menu items to show, I had to go through right-click>open file with>choose another app and select the musicbee.exe in the Portable version C:/musicbee directory folder. This time though the MB Context Menu items sit above the Windows Media ones and not replace them.....
...I may try the Desktop version again, but this time point directly to the exe.
Update: I tried again with Desktop and Store versions, Context Menu items will not show in Explorer menu.