There has been a critical error on your website - won't fix no matter what

Question

So I've got the dreaded error too it seems. Apparently it's a very common issue but I can't really seem to get a hang on the fix.

One of the plugins my theme uses is causing the error as per the log I got in the email WordPress sent to my admin email. Here's the full log

Error Details
=============
An error of type E_ERROR was caused in line 8 of the file /home/younited/domains/younitedsupport.com/public_html/wp-content/plugins/rb-essentials/metaboxes/rb_metaboxes.php. Error message: Uncaught Error: Call to undefined function rb_get_metabox() in /home/younited/domains/younitedsupport.com/public_html/wp-content/plugins/rb-essentials/metaboxes/rb_metaboxes.php:8
Stack trace:
#0 /home/younited/domains/younitedsupport.com/public_html/wp-content/plugins/rb-essentials/metaboxes/metaboxes_exec.php(200): rb_setup_metaboxes()
#1 /home/younited/domains/younitedsupport.com/public_html/wp-includes/class-wp-hook.php(289): rb_save_metaboxes(4585)
#2 /home/younited/domains/younitedsupport.com/public_html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#3 /home/younited/domains/younitedsupport.com/public_html/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#4 /home/younited/domains/younitedsupport.com/public_html/wp-includes/post.php(4260): do_action('save_post', 4585, Object(WP_Post), false)
#5 /home/younited/domains/younitedsupport.com/public_html/wp-admin/includes/post.php(687): wp_insert_post(Array)
#6 /home/younited/domains/younitedsupport.com/public_html/wp-admin/incl

Here's some additional information:
WordPress version 5.5
Current theme: Setech | Shared by WPTry.org (version 1.0.2)
Current plugin: RB Essentials (version 1.0.1)
PHP version 7.3.19

The website was running fine until yesterday on the exact same configuration. I made no changes that caused this error.

As you can guess, I have absolutely zero ideas what this means. I've tried disabling the plugin and reloading the site but it didn't work. Also, if I try to change the theme I get an HTTP 500 Internal Server Error(File "/home/younited/domains/younitedsupport.com/public_html/wp-admin/themes.php" is writeable by group) when clicking on the themes pages in WordPress.

The same site on my localhost works just fine BTW. Everything is identical between the two sites. Any ideas on how to fix this?

Answer 1

So I reinstalled WordPress on both my live and local environments and downgraded to version 5.4.2 and everything seems to be working just fine, so far.

I'll update if anything breaks again.

Answer 2

I don't think this is an answer as such but I need a bit more space than the comment box allows...

Your line here:

"Also, if I try to change the theme I get an HTTP 500 Internal Server Error(File "/home/younited/domains/younitedsupport.com/public_html/wp-admin/themes.php" is writeable by group) when clicking on the themes pages in WordPress."

Suggests that the secondary error is complaining about file/folder permissions (ie. "is writeable by group").

If the file permissions were wrong it could potentially...

1. Explain why your dev environment is ok when the live environment isn't
2. Prevent some files being loaded which would then in turn lead to undefined function errors (and others)

If you've not changed the file permissions and this has happened suddenly, I would at least check that the site is healthy using one of the well-known security plugins. You could also check if there was a difference in the permissions via cPanel, or even the command line if you have access.

It's just a thought - that line about 'writable by group' is a warning flag of sorts.