Typically when the app menu isn't showing on a mobile device, it's because the color settings for the header are set to white for both the text and background.
Here's an example of what this looks like on mobile:
To fix this, change the color of either the text or the background for the header. You can do this by going to App Settings and selecting Live App Design. Then click on the Custom Colors tab:
Note: Changing the colors for your header will affect the colors on both the mobile version and desktop version of your app.
Here's what your mobile menu will look like if you change the header's Text Color:
This is likely your best option if you're displaying a logo and you don't want users using the desktop version to see anything different.
Here's what your mobile menu will look like if you change the header's Background Color:
If changing the colors on your header doesn't help, then reach out to us at firstname.lastname@example.org or through an in-app message and we can take a look!