When you encounter your website is in offline mode, and when you will not see an error_log file that consists of all details regarding the Http Error 500 in WordPress.One possibility is that you installed a new plugin in your WordPress, just follow the few steps:
Follow the steps below:
1- Get into your hosting account, and then open phpmyadmin
2- Select the database, and export.sql file from the website
3- After that click, Search button, and put active_plugins at words or values for searching(wildcard: %), at least one word. Then choose all tables.
4-After that database will reveal active-plugin row in the wp-option table
5- Then click edit, and delete all activated plugins for the entry.
After that, you can sign in to the wp-admin account, and then activate plugin one by one. If trying this, the solution does not work, then you can also follow below-mentioned steps:
Switch on debugging to find the right cause
Increase the memory or switch theme
Ask hosting provider
Uninstall and install WordPress again
Take expert assistance from the mail, chat, or phone call support.