Keep the diffuser plugged in and locate the pinhole on the diffuser labeled RESET. Insert a paperclip or something small into the RESET pinhole and wait for a beep (approx. 3-5 seconds) The diffuser should trigger and start diffusing.
Open your app and DELETE any and all settings you currently have by sliding the setting to the left (see screenshot below) *the lights on the diffuser should turn off
Close app and re-open it.
Locate the diffuser in app and add the settings you desire.
Save settings on top-right of the screen
Save again on top-right of the screen
This should reset everything between the diffuser and the app allowing the connection to complete.