Yes, IoT OnOff works well with io.adafruit.
You need to follow some specific configuration details!
Authentication is required
Username: see at your adafruit AIO key "Username"
Password: see at your adafruit AIO key "Active key"
MQTT topic configurations
Every topic needs to start with your user name as defined in "adafruit AIO key"
Followed by "/seeds/"
Followed by a topic name of your own choice
The default DEMO configuration that comes with the install of IoT-OnOff is not compatible with the rules from io adafruit and needs to be removed before you try to connect. The connection with the io adafruit broker will be closed if you subscribe with a topic that does not follow the rules described above.