Unable to forward Gmail to iCloud

I want to forward all new messages from Gmail to iCloud. In a browser, gmail.com/mail, then Settings / Forwarding and POP/IMAP tab, then I click on the “Add a forwarding address“ button near the top and type my account @iCloud.com. Then a new window opens and I authenticate with my security key. The new window reloads with a blank screen. My Gmail is still not being forwarded. Can anyone help?