Error 500 after updating to WordPress 5.0

Internal server errors (error 500) are often caused by plugin or theme function conflicts, so if you have access to your Dashboard, try deactivating all plugins. If you don’t have access to your Dashboard, try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, try switching to the Twenty Seventeen theme to rule-out a theme-specific issue. If you don’t have access to your Dashboard, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue.

If that does not resolve the issue, it’s possible that a .htaccess rule could be the source of the problem. To check for this, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, and rename the .htaccess file. If you can’t find a .htaccess file, make sure that you have set your SFTP or FTP client to view invisible files.

If you weren’t able to resolve the issue by either resetting your plugins and theme or renaming your .htaccess file, we may be able to help, but we’ll need a more detailed error message. Internal server errors are usually described in more detail in the server error log. If you have access to your server error log, generate the error again, note the date and time, then immediately check your server error log for any errors that occurred during that specific time period. If you don’t have access to your server error log, ask your hosting provider to look for you.

I have my dashboard access. I’ve tried deactivating all plugins but still no luck.
From my erro log file, i found this information:

[07-Dec-2018 11:31:30 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:31:46 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:32:31 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:35:23 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:35:27 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:40:25 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:41:17 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:41:20 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:41:43 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 11:41:45 UTC] PHP Fatal error: Cannot redeclare has_block() (previously declared in /home/tutorial/public_html/wp-includes/blocks.php:81) in /home/tutorial/public_html/wp-content/plugins/multiple-content-blocks/assets/inc/template-tags.php on line 67
[07-Dec-2018 16:49:23 UTC] PHP Fatal error: Class ‘WP_Block_Type_Registry’ not found in /home/tutorial/public_html/wp-includes/script-loader.php on line 2421
[07-Dec-2018 16:50:18 UTC] PHP Fatal error: Class ‘WP_Block_Type_Registry’ not found in /home/tutorial/public_html/wp-includes/script-loader.php on line 2421
[07-Dec-2018 16:50:34 UTC] PHP Fatal error: Class ‘WP_Block_Type_Registry’ not found in /home/tutorial/public_html/wp-includes/script-loader.php on line 2421
[07-Dec-2018 16:51:32 UTC] PHP Fatal error: Class ‘WP_Block_Type_Registry’ not found in /home/tutorial/public_html/wp-includes/script-loader.php on line 2421

How do I resolve this

Which log entry is from the specific time of the 500 error?

Do you still have the same problem if you switch to the Twenty Nineteen theme?

I think it’s this entry: [07-Dec-2018 16:49:23 UTC] PHP Fatal error: Class ‘WP_Block_Type_Registry’ not found in /home/tutorial/public_html/wp-includes/script-loader.php on line 2421

Also, the error persists on switching to the Twenty Nineteen theme?

Try downloading WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), and delete then replace your copies of everything on the server except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.

Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

I have a strange problem… The site loads with a 500 server error since the recent update. In Firefox in a private window, and in Chrome (normal window) the site loads a 500 server error, but when I do a cache-bypass refresh it loads OK in both cases. In Firefox the site will load fine after that but not in Chrome. in Chrome, anytime I refresh or load the page I get a 500 error, unless I then do a hard-refresh, then it loads fine. if I refresh normally, it is blank if I hard-refresh it is fine. In Safari it doesn’t load at all no matter how I go about it and nothing shows up in the inspector at all (nothing in console, network, etc.) in Firefox if I open a new Private window it will load blank, until I hard-refresh again.

I have tried disabling all plugins, change theme to twentyseventeen and twentynineteen and back, manually replaced the wp-includes, and wp-admin, manually reloaded the Enfold theme we are using, used a filter in the functions to disable gutenberg, used a plugin to disable gutenberg, put a small php file in the root to make sure it’s not a hosting problem, renamed the .htaccess file.

I’m a little stumped. The necessity of a hard-refresh seems to have something to do with a cached file problem, but I can’t think what it could be. I’ve never had this kind of consistent 500 server error that could switch on and off.

@alpinisto Please follow the steps already listed above, including getting the error from the server error log.

Then, start your own thread with further details: https://www.ads-software.com/support/forum/how-to-and-troubleshooting/?view=all#new-topic-0