Unable to copy on the Books app on my MacBook Pro

I bought copies of physical books I had in the Books app so I could more easily copy/past excerpts from them. This has worked well for me in the past but this morning when I opened the app it stopped working. Right-clicking a highlighted selection wouldn't show copy as an option. See image below. Has this functionality gone away or am I doing something wrong?

[Re-Titled by Moderator]