Welcome to the Prismic community and thanks for reaching out to us.
As soon as you change the content in Prismic, Master Ref also changes which retrieve the published content only. Are you querying the API with the current Master Ref? Can you also see the changes appearing in the Prismic API browser by hitting your repo URL like this: https://your-repo-name.prismic.io/api/v2 (change your-repo-name with actual repo name). To get the current Master Ref content, you need to refresh the API browser.
I am looking forward to hearing from you back.