MyCloud Does Not Work Well with iTunes

As indicated did you also change the iTunes media library setting to point to the My Cloud?

See the following post I made in the iTunes server doesn’t work anymore thread:
https://community.wd.com/t/itunes-server-doesnt-work-anymore/95261/59

One typically has to change the media library from pointing at their local computer like the following screen capture shows:

To the following screen capture where the media library is now on the My Cloud as the following screen capture indicates: