PayPal Link keeps changing to a blank PayPal form

Under luncheonrsvp username we have a luncheon RSVP form. Under conditional we have it set to redirect to our paypal link if they choose paying by PayPal/Credit Card. 

The link works fine for a few days and then all of a sudden in changes to a link that directs to paypal but the description and payment are blank. 

I have gone back in and re-added the correct link three times now. I am just wondering if there is something else that I am missing that I should add in settings to ensure the link does not change after I add it.

Thank you! 

While I was testing I got the following error message:

The error with PayPal happens since the PayPal account used is invalid, you need to use your PayPal email address in order to successfully receive payments.

Thanks.