HTTP ERROR 500 – when clicking on Login

Error: HTTP Error 500
occurs when you click on “Login” button.

To reproduce the error, just click on Login or enter user info and click Login

When you click on register and enter name, email and password then click on enter, it registers the user but then still keeps user in the login/register page. Not sure if this is related to the error 500 that happens when you click on Login.

Please help with this
Thank you