500 Internal Server Error

Known causes for 500 Internal Server Error:

.htaccess file may have a typo.
Directory permissions on the website’s hosted directory or files settings need to be set correctly.
PHP version set for the account. Some PHP versions remove outdated functions, and your site might still be needing the old version to function. You can change the PHP version for your website.
Your site software like plugins could have introduced errors and bugs. Turning off plugins one at a time to find which one causes this issue. This is a great way to find badly coded or incompatible plugins and themes.
Account resource limits reaching abruptly. Your site might be under attack from external bots and hacking. This type of error is usually temporary, and system resources are restored eventually. In the event it is an ongoing one, the site is taken offline until the site software handling the attacks is addressed.