Paypal has not been sending payment notifications to merchants

This is a mission critical bug for any other startups that depend upon the Adaptive Payment API. That may only be a subset of Paypal merchants, but for those that do - you need to know this ASAP.

Not sure if this is related to this particular case. From previous experience, PayPal will silently stop delivering IPNs if your webhook URL ever returns a non-200 status code for an extended period of time.

It took us a fair amount of time to figure out that this was the cause of our issue -- the PayPal UI didn't indicate any problems and PayPal business customer support was unable to see the source of the problem either.

Title is Tindie specific... I wrote it for our audience but the news I thought HNers would want to know

It set off the ring detector. It looks like a false positive to me, so we'll turn that off.

We also changed the title (from "If you use Paypal, you should know they aren't sending IPNs") to make it more neutral.

If you've ever sat down and looked at Paypal's APIs properly, for instance with a view towards a proper risk analysis and/or from-scratch integration, then this should not surprise you. I did this for the first time perhaps ten years ago, and here's what I found.

Firstly, the degree of marketing bullshit that you have to push through just to get to the truth of the APIs is staggering.

Secondly, they perform backflips to avoid telling the truth about their integration options, which is to say that they're all fundamentally insecure for real time digital goods and services unless you implement IPN plus polling plus duplicate detection / additional round-trip validation calls, ie. you can't trust an IPN notification. The degree of complexity (order state tracking, IPN state tracking and duplicate detection, retry support, running your own IPN-receiving server) and latency requested here of client businesses is immense.

Thirdly, their idea of international support is pathetic. It seems that they've basically duplicated their entire business process to other countries, translated it, and then assumed that everyone in that country requires only one human language in all of their interactions: documentation, support, emails, etc.

Finally, as is widely known throughout the industry they have a shocking reputation for the arbitrary suspension and seizure of accounts and assets, with little to no recourse for those affected.

I am not surprised that Stripe has taken off. Unfortunately, that's still lipstick on a pig: fundamentally, the settlement, risk, transparency and government interaction model of credit card networks means they are unsuitable for an increasingly large volume of business around the world.