In addition, in Google Analytics, I see this message
"Data collection isn't active for your website. If you installed tags more than 48 hours ago, make sure they are set up correctly."
However, I followed these instructions over a week ago and clicked "Test" and it passed. And it still passes today.
Kind regards,
Set up your Google tag integration with Squarespace
You can measure behavioral data about your site with Google Analytics and Google Ads. If you have a tag ID starting with “G-”, follow the steps below to set up your Google Analytics and Google Ads accounts with Squarespace.
Instructions
Click the copy icon to copy your tag ID.
Sign in to your Squarespace account.
On the "Dashboard", choose the site you want to modify.
From the main menu, click Settings.
Click Developer Tools.
Select External API Keys.