I have two pages and two popups on the main menu, which is horizontal on desktop.
But, only the two pages show on mobile. They are not hidden on phone, and the popups do work on phone when called from a button.
Found it - for some reason, you have to choose "custom links", and add the popups again!
@JoeChasko oh, I'm glad you found a solution here! Always helpful to share for others who have the same question. 🙌