Changed multisite domain - ERR_TOO_MANY_REDIRECTS

Hello

I recently changed the domain for my multisite.

All the subdomains work fine with the new domain, but the primary domain/site creates an error:

This webpage has a redirect loop.
ERR_TOO_MANY_REDIRECTS

The new main site url redirects to: http://www.OLDDOMAIN.com/wp-signup.php?new=www.OLDDOMAIN.com

Any ideas?

Thanks

Elliot