Aspect ratio in Build is different than in Unity Remote (Android)

I’m just testing around with building a game for mobile but I can’t understand why the game level is displayed differently when I run it through Unity Remote and when I run it through a built APK.

In the screenshots below, you can see that the outer walls are not visible when I run the game from the built APK, but can be seen when it is ran though Unity Remote.

Built APK:

Unity Remote:

Any idea why this is? Preferably, I would like the built APK to match Unity Remote’s display.