Reactions are the simplest and easiest way to show what you feel or think about a certain message or story. No need for words or elaborations. A quick Like indicates approval while Love expresses affirmation. Convey your sympathy through a Sad reaction or communicate your disapproval with Anger. Emoji reactions became a standard, a social norm that when eliminated, something feels off.
So, what happens when Reactions are not showing up or not working in your Facebook Messenger? Annoying as it sounds, this case is happening to many users. But, let’s see if we can fix the problem and get Reactions back into your Messenger.
Ways to Troubleshoot Reactions Emoji Not Showing up in Facebook Messenger Messages

There are possible ways you can try to fix the missing emoji reactions issue on your Facebook Messenger app. You can work on each step one at a time and see if it works for you.
Clear the Facebook Messenger App Cache
Navigate first to Settings and go to Apps. Look for the Messenger app and open it. Select Storage and tap clear cache. For iPhone, you can try to offload the app and free up storage. Or you can uninstall and reinstall the Messenger app.
Long Press the Thumb Button
See the thumb button on the right side below each comment? You can long-press it to show reactions or emojis.
Reset Any Customization
Customizing your emojis is cool. But, it may be the reason why you are experiencing the problem. A quick reset can help you.
Reset your customized emojis by opening any chat on your Messenger app and long-press any message. Once the reactions appear, tap the Plus icon. Tap Customize and on the top of the screen, tap the Reset button.
Update your Messenger App

Maybe you missed out on an important update? Try to check if your Messenger app is currently running on the latest version or not.
Reinstall Messenger App
If trying all the solutions above does not give you any relief, a proper reinstallation of the app might be helpful. Uninstall Messenger properly on your device and reinstall a fresh version.
Wrapping Up
Hopefully, one of the methods below fixed the issue for you. If not, reaching out to Meta customer support may be the best idea.