I've had this same issue with my domain from squarespace linked to a Google Site, trying to get it resolved...
From squarespace support:
To summarize--upon visiting your domain, I see that typing www.moliternocarpentry.com leads me to your site, but typing your root domain moliternocarpentry.com (without the "www") does not.
We’re currently investigating an issue with root domains (without the "www") not redirecting to Google Sites—thanks for reporting this to us. Our Engineering teams are prioritizing a fix for this as we speak.
There are many variables that we test against before we release a fix, so we can’t provide an exact timeframe for a resolution. We can’t always follow up personally when a fix is released due to the volume of reports we receive for this issue.
That said, these reports are crucial for us as we improve our platform. If you notice any other unusual behavior, please contact us again.
In the meantime, you may continue using your "www" domain, or you may also choose to change and share your built-in domain as well:
