I am having a similar problem as well. I’m new to WordPress. I just installed my own theme, and things are working fine. Under each post it’ll ask to leave a comment; however, if you try, you are sent to a page that has the post but no comment box. My blog is at https://royal-hours.net is you are wondering what I am talking about.
I can’t think of what the problem could be, I have comments enabled in Settings and on individual posts. I think it may have something to do with the theme, because when I change the theme back to Default, it works, but I cannot figure out exactly what it is in the new theme I built.
