This is still not working in Sandbox as of this writing!!! I would like to raise this up because it seems nobody from eBay side is taking care of fixing this. I believe there are great applications relying on Platform Notifications because for one, this does not count to the limited Trading API Calls thus saves API call requests, and of course the event is close to real time, like when an order is made, the application can then receive the order data just seconds after. This is advantageous for a lot of inventory management applications for instance. If this is not fixed in Sandbox, then eBay would want us developers to test in Live environment which they would benefit because it would be live payment transactions where fees are non-refundable.
I have been running "Platform Notifications" for over two weeks now on "production". On December 9th (9 days ago), I received 22 notifications which is only a small portion of what I should have received. I have not received a single notification since. I never received a single notification from the sandbox. I have personally decided to not rely on Platform Notifications as they do not seem to work at all and ebay's support on this matter is ridiculous as all they ask me to do is pay them $75/hour to fix their issue?? What kind of support is that? Has anyone got Platform Notifications to work consistently? I have not. I get maybe 1-2% of the notifications I should be getting.