I've omitted many of the data tuples from the URL for the sake of brevity, but they're all obvious ("return", "item_name", "amount", "no_shipping", "custom" and "invoice"). It has worked without any issues since at least 2007, but sometime late last year, it stopped working. Not that PayPal sent me any kind of sensible errors or friendly notifications that it wasn't working mind you - no, I found out because I started losing sales. What happens now is the user gets transferred to a bizarre PayPal page that says "We're sorry, things don't appear to be working at the moment. Please try again later" with an error code shown in the URL bar that looks like:
I have looked everywhere for information on what has changed, and what I can do to fix it, but while I've seen plenty of people reporting the problem, I haven't seen anyone reporting a solution. I can't even find any information on what the error code means: my PayPal account is definitely a business account, is not blocked or restricted, and is functioning normally apart from this one issue.
Just to clarify: this isn't a button - I handle my own ordering workflow, and when it comes time for the customer to make a payment, I construct a URL in my web server module that contains the details and the amount to pay, and redirect it to PayPal. I haven't changed anything in the process for several years, and it has always worked fine.
Does anyone have any idea what this error means, or even better, how I can fix it? My entire business is currently stalled because I can only accept payments manually (i.e, by having the customer send me the money separately).