Try checking in your root directory of the WordPress instance if there’s a file called “error_log”. You can open it with any editor and see if there’s any error, especially marked as Fatal error. This maybe the cause of some problems.
Simply edit wp-config.php file in your root directory of the WordPress instance and locate
define('WP_DEBUG', false); eg: https://d.pr/i/AguD4C and replace with these lines:
define('WP_DEBUG', true); define('WP_DEBUG_LOG', true);
After doing this, in the /wp-content/ folder, there should be a new file called debug.log .You can monitor this file to see if there are any fatal errors inside.
If you want to have the errors displayed on the site, add this constant
define('WP_DEBUG_DISPLAY', true); next to the other ones.
Make sure to DISABLE after you’re done debugging!
Read more about Debugging in WordPress .