We are also seeing exact same result today, since at least 1:15pm CDT.

Not that it's a great solution at all, but I commented out my changes to use notarytool from a few months ago and restored my use of the old process using altool and just successfully submitted and notarized my bundle! Haha. So @gpdawson that might be on the menu as a temporary workaround. EDIT: confirmed -- I switched my release to use altool in order to get new builds available tonight. Seems like just a month back or so I was getting deprecated warnings and couldn't actually get a successful result with altool, and now it's back. Never a dull moment...

Just an FYI that this is occurring once again-- use of notarytool w/ app-specific password is consistently failing today ("Error: HTTP status code: 500. Internal server error. Error communicating with authentication service. Please try again at a later time."), whilst altool is still available and working using app-specific password.