Good evening Alan and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the error 500 message you are receiving.
I would love to help you with this topic.
The first thing I would do is go through the following guide: http://www.wpbeginner.com/wp-tutorials/how-to-fix-the-internal-server-error-in-wordpress/
The most common culprit is the .htaccess file.
I believe that once that is done, you should be able to adjust your settings to your liking.
Also, if you are able to, as a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Let me know how that goes.
Best regards,
Geoff B.