Node red issue when inject message, the MQTT publish node disconnect

i have a issue when i'm trying inject the node, the MQTT publish node( the broker that i'm using: [io.adafruit.com]) will always become disconnected and the data is not been updated into the my adafruit feeds . I also tried it using node red fred sensetecnic but its still give me a same problem .So, can i know why this thing happen and do you have any solution for that?. Thank you.
mqtt%20server

If it gets disconnected when you try to publish, that suggests you are trying to publish to a topic you are not allowed to use.

The valid topic structures are documented here: https://learn.adafruit.com/adafruit-io/mqtt-api#topics-15-4

i already change the topic but it still give me the same problem. Is it this issue occur because of the broker server that i'm currently using?.

Are you using a free or paid account at adafruit?
Have you ever been successful at send/receiving a message?
what does your topic lookalike (xxx out your username)

What platform are you running NR on?
If it is a Pi, have you thought about installing MQTT on it?