redirect_uri_mismatch when using Google Analytics +

I'm trying to set up Google Analytics + on my site network. I have it network enabled. I click on "set up Google API project" as in your instructions. I enter my data in the 3 fields. I click Authorize, and I get this error from Google:
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400. That’s an error.

Error: redirect_uri_mismatch

The redirect URI in the request, https://artlauncher.online/, does not match the ones authorized for the OAuth client. Visit https://console.developers.google.com/apis/credentials/oauthclient/(url shortened to protect code numbers)/ to update the authorized redirect URIs.

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Request Details

That’s all we know.
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Any ideas what's wrong? I suspect it's the Request URL setting. Your instructions say:
"5. Important: Enter the URL of your primary network site in the field marked Authorized Redirect URL."
I entered "https://artlauncher.online". I'm guessing there needs to be some path with it, but your instructions don't say which path is prepared to accept the callback from Google. Please advise.