Hi. When I start a new listing, it fills in with the master I have set to default. It also has the option to change sites and put in a different master profile.
What about when you select from the middle - where the drop-down is - and you can choose which master profile you want to use there? Does that work?
If not, I'd file a support request, from the Help link at the top of any page. It shouldn't be grayed out so you can change sites. Maybe there's a glitch they can fix for you.
I'm sorry that's not much help. I don't know what else to tell you to try though.
Please do feel free to come back here and post. I'd appreciate knowing how it works out.