You have one page where you want to use a different menu than the one you set as main menu? No problem!
Scroll down to the page/post options and select the menu “general” tab. Switch from Default to whatever style you prefer. Maybe you need to check what you have set as default in the “Miami Options”.
In the menu “content” you will find all available menus.
If you have not created an extra one go to “Appearance”, “Menu” to do so.