Hi,
This happens because the app no longer supports automatic album information lookup for CDs. Microsoft ended its license with their metadata service provider last December, and with that service discontinued, the app can no longer retrieve the album information online. As a result, the album and track details may now appear as Unknown.
That said, you can try an alternative like this one, which based on other users who suggested it, has a feature that can automatically retrieve album and track information.
Disclaimer: This is a non-Microsoft site. The information seems reliable, but be careful with ads. Research any product before downloading.