Can't display the edit button on smartphone

When users open Collabora file on iPhone SE, there are some devices where the edit button appears in the bottom right corner and others where it doesn’t. The iPhone SE does not show the edit button, but it appears when the user changes to desktop view mode. The same is true for reducing the display font size of the device.

What’s the difference between an iPhone SE that shows the edit button and an SE that doesn’t show it?

Collabora 6.2.8, Loolwsd 4.2.1, Collabora app 3.5.3, NC 18.0.3