Answer by Steegle - In short, it's a misinterpretation that you need to be able to reject all cookies,
https://support.google.com/sites/thread/166367292
and
Answer by Perjury
https://support.google.com/sites/thread/164674361
Answers by Perjury
https://support.google.com/sites/thread/74845839?msgid=74853511 and
https://support.google.com/sites/thread/184495005?hl=en&msgid=184529862
Answer by Perjury
https://support.google.com/sites/thread/178651827?msgid=178753259
Either:
a) You are not signed in with the owner account
or
b) You are using Google Workspace in which case the process is slightly different
see
https://www.steegle.com/google-sites/how-to/map-domain-web-address-g-suite