Resolved in this instance using this procedure:
Open SSMS and connect to the database server
Browse to the portal database then (expand tables) find dbo.PortalAlias right click and select 'Edit Top 200 Rows' then modify / update IP instances with your resolvable IP address.
corrrespondingly modify dns settings for your domains with your provider.
THREE step 1. go to IIS on your server, stop your site, reset site IP bindings 2. go to the location of your dotnetnuke site folder on your server and open web.config (modify trivially with a space at the bottom, save, undo re-save - this induces iis to reset ip bindings) 3. go to IIS and restart your site.
Browse to your site to check your configuration and re-instantiation.
Credit to this answer by Chris Hammond - DotNetNuke Tip Modifying your Portal Aliases (asp.net)