Cannot get domain mapping to work

I would like to request support access please. I have tried everything to get domain mapping to work and having no luck.

WP multisite 4.)
Godaddy Ultimate shared hosting
Dedicated IP address
Multisite set up as subdomain and working fine.
SSL wildcard set up and working on multisite.
WP HTTPS / SSL setup and worked ok
Domain name A record pointing at WP dedicated IP address
Mapped domain name to subdomain which is valid OK
Website showing a redirect loop in browser.

I have granted support access to you already.

Would really appreciate your help checking my settings and helping to get the domain mapping working as I have another LIVE client site that I need to launch urgently.

Many thanks,

Sean.