Domain access - prevent redirecting to default domain on account creation Drupal 7.36 &amp; Domain access 7.x-3.x

I have 2x domains running curtesy of domain access. Each domain has been set up for 2 specific groups of users. The idea is that each group can create accounts, log-in and access content on their respective domain. Setting up the default domain worked fine. But, when users attempt to register on the second domain, they are redirected to the default domain instead, causing confusion.

I have Domain Strict enabled – plus I have tried Domain bonus, but the solution does not seem to be straight forward. 

How you I prevent this from happening?
Apologies - it turned out that the default domain had been set as the base URL in the settings.php file. When a user requested an account, they were being returned to the default domain homepage