After about an hour scouring the internet and delving into Google Developer pages way above my pay grade...
The answer for me was that I needed to use my SquareSpace "built-in domain" instead of the domain name I registered. So dont use your fancy domain like www.ilovecats.com - just use the random website name that SquareSpace gave you when you started building the site. It's available under "Settings_Domains" and it's the "built-in domain."
Godspeed Squarespacers!