I tried adding Vanguard yesterday using the main Vanguard https://investor.vanguard.com/corporate-portal option and also got the:
Technical Error at Vanguard
We’re unable to connect your account at this time. Please try again later. If the issue persists reach out to our support team via chat at https://my.tillerhq.com
However, if I use the Vanguard Group (Quicken) https://investor.vanguard.com/home option - it works.
Here’s the Institution Alerts for Vanguard options at this time (both above options have alerts):
Visiting the Vanguard “corporate-portal” URL link in a web browser - it does not have a login link.
The Vanguard Group (Quicken) “home” URL does have a login link, which matches the URL I use to access Vanguard directly.
It does seem strange that the main Vanguard option doesn’t work though 