If you’re using Safari on the Mac, you can try disabling ‘prevent cross-site tracking’ and ‘hide my IP address’ if they are enabled.
I’m skeptical it’ll make a difference, since you tried it on a Chromebook, but it doesn’t hurt to try. This is what I did to get bonds to show up on Vanguard’s website, otherwise I had a blank page.
You could also try calling Vanguard, but that’s a bigger commitment. If you call them, I’d definitely select the callback option and make sure you have the next hour or two free.