When attempting to connect to Vanguard's OFX server, I now receive an HTTP status code of 302 and the following location response:
  "location": "http://error.vanguard.com/telecom-bounc … rcode=3004",
  "server": "BigIP",
  "connection": "close",
  "content-length": "0"

If I attempt to go to the URL specified in the location, I get a website not found error.

This just started happening a few weeks ago.  No problems previously for a few years.