The RSVP itself is working.
I watched the video and read the instructions. I saved the config file and uploaded it. WordPress found the file.
In the file I tried both the API info for the sandbox settings you provided at the top of the config file, and I tried the client's API info for their Paypal account.
When we hit the 'NEXT' button in the RSVP process it does not go to PayPal, it goes directly to the website's homepage.