New primary key and broken images

Hi,

I’ve been trying to make it so subsites on my wordpress install can use external domain names, i.e. wwww.primarydomain.com for a blog hosted on wordpress.test.######.###/####. If I keep the wordpress.test.######.###/##### format as my primary domain name, my pictures and everything work. If I change my primary domain name to https://www.primarydomain.com, none of my pictures work due to a 404 not found error. It’s searching for the pictures in https://www.primary.domain.com/files/$blogid/ etc which returns the 404. Is there a step I’m missing on this or am I going to have to use nginx rewrite rules in order to manipulate the request as it comes in?

Thanks for your help on this,

Eric