Q: I can't reply to a group message

I need help! I can't reply to a group message suddenly. I left the group, but then someone added me back. Instead of ccoming up as 'kylie added you to the conversation' it comes up as if they added another contact, my number, and when I go under details everything's still greyed out, but now my number's is included on the detail page when it never was before. Any ideas?

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