Thanks for letting us know, Qpoiuytrew,
Are you referring to the Messages app on your iPhone? If so, this resource will show you how to troubleshoot sending and receiving messages on your iPhone: If you can't send or receive messages on your iPhone or iPad - Apple Support
"If you see a red exclamation point
If you try to send a message and you see
with an alert that says Not Delivered, follow these steps:
- Check your network connection.
- Tap
, then tap Try Again. - If you still can’t send the message, tap
, then tap Send as Text Message. Messaging rates may apply. Contact your carrier for more information.
You can set up Messages so that it automatically tries to send messages as an SMS when iMessage isn't available. Go to Settings > Messages, and turn on Send as SMS."
If you're referring to an app that is developed by someone other than Apple, you can reach out to the app developer for help with their app as outlined here: How to contact an app developer - Apple Support
We hope this helps you.
Take care!