Good evening Holly and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the error 500 creeping up on you.
I would love to help you with this topic.
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/
Secondly, would it be possible to share the Google Calendar URL you are trying to import.
Hang in there!
Geoff B.