ILIA

This is still a problem for me as well; I can set up redirects on any subdomain name I want, but not for the root domain somehow, getting that totally unhelpful error message. I need to use domains as redirects to our Google Sites, which I have been able to do on Bluehost and on Google Domains, but I would be concerned if after Google Domains is fully transferred to Squarespace I would lose that capability.

Just finished a chat with support.  Had to delete the default DNS info under domain management then it let me add the redirect.