Ah yeah I believe this problem might start after the 2nd time the action is invoked. I recall being able to get the "correct" (non-error) message on the first attempt, but after that, I got the error.
I can confirm that the original machine that I experienced this (having upgraded from 1909 btw -- perhaps that also has something to do with this?) -- is not Insider, so we can definitively rule that out.
Finally, this is what I see on my insider machine so it doesn't look like the builds are downloading.
I appreciate you taking the time to help debug/diagnose this issue. Looking forward to hearing about your 2nd try. It would be interesting to know if you are using a clean 2004 install or if you upgraded from 1909 as well. Thanks again!