the 500 Internal Server Error is a default error tht will be shown if error reporting is turned off.
It is a very vague error and is impossible to troubleshoot.
We need to know what the real error is to be able to have an idea of what is wrong.
You may be able to add the following code at line 1 to display the error:
if that does not display the error, you will need to contact the host to gain access tot he servers error logs to find the error.
Once we know the error, we can begin troubleshooting the cause.