Hi Roxanne,
Thank you for your reply.
Yes, I had Elementor disabled. The problem was still the same.
The add-to-cart button which is visible, is created with Elementor.
The add-to-cart button provided by WC itself is not visible in the frontend (see the blank field marked red in the screenshot) above the Elementor button.
https://snipboard.io/aC2zpG.jpg