"This invoice has already been paid. For more information, please contact the merchant."

#1

I’ve been using S2MemberPro without major issue for 3 years then suddenly out of the blue yesterday customers all receive this error…

“This invoice has already been paid. For more information, please contact the merchant.”

I’m using S2Member button code (not Pro Forms) and it happens after they get re-directed to Paypal.

The S2MemberPro help files I found (here: https://www.s2member.com/forums/topic/invoice-already-paid-error/) suggests this…

Is it possible that your site (i.e. another plugin maybe), is caching the HTML that is produced by this Shortcode? That’s what I would suspect at this point. The same button is being clicked by each visitor to the site (i.e. the invoice is always the same)?

I’ve not added any new plugins and I’ve tried isolating them one by one to figure out which is causing the problem without much luck.

Every time I think I’ve found the conflicting plugin further tests show that it’s not that plugin.

It now seems to be hit or miss whether a customer will be able to successful pay and join the membership site without getting the error message.

Does anyone have any suggestions to the cause and how to fix this?

Thanks for your help.

#2

Hi,

I’m having the same problem. The site I maintain has been successfully selling access to online guides using PayPal ‘Buy Now’ buttons for 3 years or so. We are now getting reports of some people having the same issue as SEW: ‘This invoice has already been paid.’

For us, the problem is intermittent and not universal.

I had though it might be because I’d recently installed the WPMUDEV Hummingbird cache. I had deactivated that but the problem persists.

Does anyone have any suggestions as to why this might be happening?

Thanks.

#3

We switched to the using the S2 Pro Form and it fixed this problem but then caused a new (also intermittent) problem…

…now when people click the Paypal buy button it’s hit or miss whether they will actually be sent to Paypal or if the sales page just refreshes with no sale going through.

We thought initially it would just be a plugin conflict but we haven’t been able to diagnose any conflict and even with all plugins turned off it still happens.

S2Member haven’t provided any answers or help.

#4

Did either of you manage to get this sorted? I’m looking at s2member for a new site but wary of the recent dev changes and seemingly unsupported issues such as this.