From my reading of the code:

• the debug message ("Hash check request failed") comes from a failed CheckResultValue in the call to RequestModerationCheck::requestModeration
• requestModeration is creating a payload with the URL for the file (createModerationRequest), and not the file itself. (That means PhotoDNA needs to make a request back to MediaWiki. I saw some discussion in another task about whether it would be preferable to just transmit the file -- that way we avoid issues like Commons not responding to the PhotoDNA request for whatever reason.)
• Looking at the logs for that requestId, the error is T336205: Debug Error: The given file could not be verified as an image

So, I think we could close this as a duplicate of T336205: Debug Error: The given file could not be verified as an image?

my understanding, and granted it seems a lot of the information I was given seems to be a bit off, was that we were sending hash strings to PhotoDNA, so now I am totally gonna have to go back and review what I thought I knew.