I had this same problem. One person in my contacts was highlighted in blue and when I tried to text them, it would say sending a "chat" not a text. I would hit send and then they wouldn't get anything. I solved it by uninstalling the app. Then (in google play) turning off automatic updates, then reinstalled the app. I haven't updated it since, because the first time I uninstalled it, I didn't turn off auto update and the update when through over night and I had the same problem all over again -- so the only way I can get it to keep working is not to update it. I guess eventually, I will have to update it - -but I'm trying to wait until they fix this issue.
It's important that all your text messages are received. I apologize that you are still experiencing issues with sending text. With issues still persisting, we do suggest temporarily switching to the native application on your device. With Samsung, please go to the application tray and navigate to the native messaging application called "messages". If using Lg, the native application is called "messaging". If using Motorola or Pixel, the application is called "messenger". Please let me know when switching if all text are sent and received.
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