Thank you for your reply.
Interestingly, when I add the <–read more tag–> with the WP editor as you suggested, (which incidentally I never had to do before and still got the <read more…> button showing up in the other posts) it appears in the post, but once again is missing when viewing from the home page. I also noted that a spelling error which was previously corrected in the post, persists in the excerpt. Even if I delete the entire first paragraph in the post, the excerpt persist showing the now non-existent paragraph. This is totally weird! I tried cloning the page, same result. I’m now thinking just deleting the post completely and rewriting it from scratch.
Any more ideas? Is there a way to “flush” the excerpt?