Comments are displaying like this in our staging site but are working fine in the live site.

I've deactivated the plugins I had installed since copying live to staging, but it still isn't displaying correctly. I also deactivated the theme (BuddyBoss), but that didn't help either.

At first the site was displaying a 'critical error' message and this was in our error logs:

[Fri Jul 30 16:02:50.849750 2021] [php7:error] [pid 29866] [client 86.137.51.221:55780] PHP Fatal error: require(): Failed opening required '/nas/content/live/onehe/wp-content/plugins/wpdiscuz/themes/default/comment-form.php' (include_path='.:/usr/share/pear/php:/usr/share/php') in /nas/content/live/onehestaging/wp-includes/comment-template.php on line 1554