Problems importing PDFs to Books on my MacBook Pro

Every time I try to import a pdf file into the books app on my MacBook Pro (M1, Sequoia 15.0.1) nothing happens. I'm fairly sure this is only happening in the last month, since upgrading to Sequoia.

I've found a workaround which involves emailing myself with the pdf as an attachment. Then I open the mail on my iPhone and share the item to Books from there. Not very elegant, but it works.

Does anybody have a solution to cure the original problem?

[Re-Titled by Moderator]