What is a 500 Internal Server Error?
Internal Server Error 500 is not WordPress specific. This can happen with any website running on a web server. Due to the generic nature of this error, it does not say anything to the developer.
Step 1. Check for a corrupted .htaccess file
You can do this by renaming the .htaccess file to something like .htaccess_old. To rename the .htaccess file, you will need to connect to your site via FTP or the file manager application in the cPanel dashboard of your hosting account.
After renaming the .htaccess file, try visiting your site to see if that resolves the issue. If so, then give yourself a pat on the back because you fixed the internal server error.
Before proceeding with other things, make sure you go to the Settings page »Permanent links in the WordPress administration area and click the save button without making any changes. This will create a new .htaccess file for you with appropriate rewritten rules to ensure that your post pages do not return a 404 error.
Step 2. Increase PHP memory limit
If you see the internal server error only when you try to log in to your WordPress administrator or upload an image in your wp-admin, you should increase the memory limit by following these steps:
Create a blank text file named php.ini
Paste this code Name: Memory = 64 MB
Save the file
Step 3. Disable all plugins
If none of the above solutions worked for you, it is likely that this error is caused by a specific plugin. It may also be a combination of plugins that do not play nicely with each other.
Go to the file manager and rename the plugin folder. All plugins have been canceled automatically
Step 4. Re-upload core files
If the plug-in option has not fixed the internal server error, you may want to re-upload the wp-admin and wp-includes folder from a fresh WordPress installation.