Problem with connecting domain from namecheap

I have a problem with connecting my domain from
When i add domain in webflow hosting tab - only one domain appear (instead domain with www )
When i publich - it show empty page

I already read all webflow documentation and all topics about it but can’t fint solution
Could anyone help me with this ?

Click on Add a custom domain again and add the domain with the www. Also once done hover over the line and click the Make default icon. then publish again.

When i try to do it - appear following error

Can’t understand what is wrong