I am using Instanttvchannel in Direct Publish mode to create my channel. My content works great. I originally used one of my generic graphics as a placeholder for the thumbnail URL on my individual videos. Then I created appropriate thumbnails from stills in each piece of content, made them the proper size, 800x450, copied them to my server and changed the thumbnail URL on each video content entry. I then did a refresh of my feed in ITV and went to my Roku Developer account, ensured the feed had ingested (no errors), then loaded my channel. Now that I've changed from my original placeholder thumbnails to the real ones all I get is a big question-mark in the thumbnail box for each video. If I put back the original file in the thumbnail URL and then reload my channel I get that original thumbnail back. So it looks like once you set a thumbnail URL, it wants that to be permanent and won't let you change it.
I ensured that in the Content Editor in ITV the proper thumbnails appear perfectly for each video. I can also copy/paste the URL into a browser and the correct thumbnail image comes up. So I know it's reachable and the URL is valid. Yet if I change the thumbnail URL in the ITV Content Editor from the original one I used as a placeholder, to the correct one for the video, I just get a "?" when my channel loads rather than the thumbnail image. I also noticed that if I totally blank out the thumbnail URL and re-push the feed to Roku, then relaunch my channel, it comes up with that original placeholder thumbnail image.
So....everything looks good in the Content Editor in ITV, the feed is being ingested on m Roku account without any errors, yet the only thumbnails I can get are whatever I originally entered for each video. Does it not re-load the thumbnail if the URL changes? It appears that once it has loaded a thumbnail for a video the first time, it caches it forever. If that is indeed what's happening, is there a means of clearing that cached value so that it re-reads and re-loads the thumbnail from the modified thumbnail URL?
Everything else on my channel seems to work perfectly. It's this one odd glitch with the "?" thumbnails that I haven't been able to resolve.
The new thumbnail is either in an improper format (saving a PNG with a JPG extension) or the link is incorrect. If you want to send me the feed address in a PM with the image link that is not working I will check it out.
I don't think it is a cache issue because you get a ? when you change the address.