Greetings JT1995k,
It appears the number you're messaging doesn't support iMessage, which is why the blue arrow isn't appearing.
To help troubleshoot being unable to send messages, test after restarting your iPhone and after ensuring iOS is updated, as taking these steps can help clear up software issues. Check out those suggestions and more in the article below:
If you can't send or receive messages on your iPhone or iPad - Apple Support
"If you still need help
It appears you're attempting to reply to an automated system for a survey. If that is the only message thread which is experiencing the behavior after taking the steps above, then it sounds like the issue may be with the system used by the service sending you the survey. Reach out to their customer support for further details.
Kind regards.