I can see from your post that you're unable to see emoji that are sent to you. I know its important to see the full content of your messages and I'd be happy to help get this working again. Just to be sure, do you have this problem if you send emoji to your family and friends? Does this issue only occur within the Messages app? Have you had a chance to power off your device? If not, you'll want to press and hold the Top (or Side) button until the slider appears. Then drag the slider to turn your device completely off. After the device turns off, press and hold the Top (or Side) button again until you see the Apple logo.
You can use the steps in the link below to navigate to you Keyboard Settings where you can remove the keyboard. Once removed, restart your device and re-add. Let me know if this works.
Use emoji on your iPhone, iPad, and iPod touch
Thanks for using Apple Support Communities.Don't see the emoji keyboard?
If you don't see the emoji keyboard, make sure that the emoji keyboard is turned on.
- Go to Settings > General > Keyboard.
- Tap Keyboards.
- Tap Add New Keyboard.
- Tap Emoji.
Regards