I created a copy of a clients’ WordPress site in a hidden folder. It uses a copy of the database, not the live DB. On the copy, I upgraded WordPress from 3.9.2 to 4.0 and upgraded all plugins. I also created a new page in the copied site.
While this was going on, 3 new comments were posted on the live site all on the same post and were not yet approved. I created a temporary post category and used that as a condition to export the post (along with its comments). Next I imported the post into the copied site. I checked and the import overwrote or replaced the earlier version of itself that was already in the DB. In the WP Admin, I verified the new unapproved comments were indeed there. I navigated to the post in the WP admin and unchecked the temporary category, resaved the post and then deleted this temporary category.
At this point I probably should have looked at the post itself but I didn’t think to do so - I figured since it was fine in the admin,o it should be fine in the website. So I used a plugin called Duplicator which I’ve used many times before to download a copy of the modified/updated site, I erased the live site and then used the Duplicator installer to copy my modified version of the site into the live folder/database (it automatically overwrites the target database).
I tested and everything seemed fine but had not looked at any posts that had comments. A day later I discovered that any post that has a comment results in a 500 Internal Server Error when I try to open the URL. It displays fine in the WP Admin and I can see all the comments in the WP Admin but I can’t open the post itself.
I’ve searched for a solution and the only thing I can find is to rebuild the htaccess file. I’ve tried that but it does not fix my problem.
Can anyone give me some advice here of how I can fix this? I’m really desperate to get this repaired ASAP.