Thank you for the information. The error 500 is an internal server error which does not give the actual problem that might happen. The best way to get around this is to enable the WordPress to debug mode so that we will get a better error reporting than 500 to help us understand why this is happening in your environment.
To enable the WordPress to debug mode please kindly read the article below:
If there is no obvious error in the UI or the Google Chrome Developer Toolbar console then you will need to contact your hosting service provider and ask them to check the error log to find out the root cause of the issue.
The common issues that might occur are mentioned in this article below which I encourage you to check:
There are 2 more possible issues which are not mentioned in the article above that can be the cause: