Roku Direct Publisher is a great product and its free, but it has its limits and drawback, one of them is that it takes hours for the new content to update and it’s very hard to troubleshoot.
You will be spending a lot of time to troubleshoot if you are creating your content feed by hand, and you are not familiar with RDP.
That said, If you want more robust solution to manage your content feed for RDP, then I would recommend our OTTfeed.com platform, it was designed to solve this exact problem and much more.
Also, We have custom Roku app that is similar to RDP but with more features, I plugged your feed and it looks good (see screenshot below).
However, when I view it on a ROKU, all it shows is a SEARCH, INFO and not much else.
There are two potential issues happening here.
It takes upwards of 6 hours for Roku to ingest a json file and make it active.
A search of this forum will reveal that other developers have reported the same issue. If you still have this problem, contact Roku Partner Success. They should be able to fix the issue.
JSON sample that you have is a good working sample, the issue is with Roku Direct Publisher, contact Roku dev support to fix the bug: https://developer.roku.com/contact