Check that you don't have a system setting that enlarges the screen, effectively making the device screen too small. Lupa fits in most devices in most configurations but there are some cases where we stub our metaphorical toe.
If you are using an iPhone 6 / 6s / 7, see this article on Apple's support site for how to set / unset Display Zoom. Other device manufacturers have similar features. If you need help, send us a message and we’ll figure it out with you.