I've been working on creating a custom master page for a customer and it is working successfully on my dev server. However when I try to added it to the customer's server and change master pages it always appears as Seattle.
Both the sites are Team Site templates with publishing features enabled on the Site Collection and Site level.
It appears as if the customers site is Stuck in Seattle, when I try changing it to the OOTB Oslo page it still remains as Seattle. I think there is an issue with their site.
Has anyone heard of this issue before, if so how do I fix it so it will use the custom master page?
Note: Yes I have upload the custom Master page correctly and I can see it on
Update: Change Site Master Page