@TeamYouTube I’ve been trying to change my banner for around 1 week now and I keep getting this message everytime?pic.twitter.com/YawQy8EofK
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That's strange. Could you try clearing your browser's cache and cookies to see if that makes a difference? Here's how: https://yt.be/help/V8qD . Also, try checking it on different browser/Incognito mode. Let us know if that does the trick.
I’ve just tried it and I’m still getting the same message 
Thanks for trying those steps. We'd recommend sending us a feedback report directly from your YouTube account with these steps: https://yt.be/help/RYwc . You may not get a direct response, but we do review everything to investigate and fix issues.
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