Mirror screen is missing from my icon

Hi 123chloe,

Welcome to Apple Support Communities. We understand that you're having an issue with an app on your iPhone. We'd like to help.

Can you tell us more about what you're missing? Is this referring to an app you downloaded from the App Store or are you referring to AirPlay that would allow you to mirror your device? If it's about AirPlay, this may help:

Use AirPlay to stream video or mirror the screen of your iPhone, iPad, or iPod touch - Apple Support

Stream video from your iPhone, iPad, or iPod touch to a TV

1. Connect your device to the same Wi-Fi network as your Apple TV or AirPlay 2-compatible smart TV.(1)

2. Find the video that you want to stream.

3. Tap AirPlay . In some apps, you might need to tap a different button first.(2) For example, in the Photos app, tap Share , then tap AirPlay .

4. Choose your Apple TV or AirPlay 2-compatible smart TV.

To stop streaming, tap AirPlay  in the app that you're streaming from, then tap your iPhone, iPad, or iPod touch from the list.

(1). SharePlay doesn't support AirPlay 2-compatible smart TVs. To stream video with SharePlay, use an Apple TV. 

(2). Some video apps might not support AirPlay. If you can’t use AirPlay with a video app, check the App Store on your Apple TV to see if that app is available.

Hope that helps.

Take care!