Emoji keyboard doesn't appear while iPhone mirroring

If Control + Command ⌘ + Space isn’t triggering the emoji popup, here’s a surefire way:

Step-by-step:

1. Go to:  > System Settings > Keyboard
2. Scroll down to Input Sources
3. Turn ON: “Show Input menu in menu bar”
4. 
5. Now you’ll see a keyboard icon in the top-right menu bar
6. Click that icon → Choose “Show Emoji & Symbols”

Now, see the pic below

I am still not clear which app you are using where you need the emojis. iOS Notes, iMessage, iOS email etc

On iMessage, there is a simpler way to pop-up emoji, See the GIF below

Click the emoji section -->