I got the same message and used the option in the message to report to Micrsoft that this is safe software in order to update Windows Defenders list.
To me this looks more like something is new in Windows Defender than in Quicken. As in, it checked that it is OK to send a file to them to check it out. I would suspect that most anti-virus software send files to their servers to check out without asking. This is probably the result of someone complaining about such, and Microsoft prompting you to make sure it is OK. You will notice that in no way did it actually say the file had a problem. Note I just got the same prompt, so I know that Windows Defender didn't find anything wrong with the file I let it send.
I suspect your problems are directly related to what the Windows Defender prompt. I suggest that you post yours as a new question so that it gets the right visibility. Select New Post from the top of the page.
Is your system up-to-date on Antivirus definitions and/or other Windows System Updates? Have you contacted Windows Support for assistance in this matter?
For what it's worth, I did the update today and didn't get this prompt from Windows Defender. I suspect that people that got this prompt earlier and sent the file to Microsoft resulted in it being put on the "whitelist" for future installs.