500 Error

Hi there,
I had the form on this page set up so that when someone completed the form, it would redirect them to PayPal, write the contact form to a database, and write the same info to a Google Sheet. However, when this plugin is activated, I get this error:
https://bbabc.net/join/#wpcf7-f111-p50-o1
“bbabc.net is currently unable to handle this request.
HTTP ERROR 500”

I have turned off all other CF7 plugins.

It was working until May, and is no longer working. Can you please let me know steps I can take to make it function again?

Thanks!
Loren

The page I need help with: [log in to see the link]