Why is my iPhone 6s not allowing me to sign into iCloud?

If you can't connect or sign in to iCloud, Apple has a list of things you can try in the document If you can't connect or sign in to iCloud - Apple Support

If you are using a VPN, try turning it off and see if you can then log in. E.g., AppStore - Apple Community

For more assistance try the iCloud Support web site --> iCloud - Official Apple Support

If you still have problems try official Apple Support. Click here --> Choose your country or region - Official Apple Support Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

or:

Contact Apple for support and service --> "See a list of Apple phone numbers around the world."

Click here --> Contact Apple for support and service - Apple Support

I have no idea what that means.