Custom URL access portal, but the logo and entered URL back to zoho url

Custom URL access portal, but the logo and entered URL back to zoho url

I'm paid plan. 

I have already set up a CNAME and successfully point to business.zoho.com, the URL correct.

However, I found the LOGO still appear ZOHO logo, moreover, once enter insides, the URL is back to mail.zoho.com.

How can i settle this problem ? Thanks and regards

Kevin