Juno access only with VPN on?

[Clubwich]

I have an ancient Juno email account that I still use for some things. Recently I've been having trouble accessing the site, but I accidentally discovered that I had no problem accessing it if I logged into the VPN I use to connect remotely with my office computer (which is a PC in another state) and used the browser on the PC. Eventually I discovered that I didn't even have to log into my PC; all I had to do was turn the VPN on in System Preferences, and then I could access it through my home laptop. Does that make any sense at all? I haven't had any issues with other websites.

I use Waterfox at home (but have tried Safari); on the PC I use Chrome.

Mac OS HighSierra 10.13.6
MacBook Pro
Model Identifier: MacBookPro14,2
Processor Name: Intel Core i5
Processor Speed: 3.1 GHz