First, make sure you have reviewed our general speech recognition tips.
If the app repeatedly fails to hear the trigger phrase when it is spoken, try increasing the sensitivity. You will find the settings for the regular and Alexa trigger phrases in the Trigger Phrases section of the settings. You may need to experiment to find a setting that allows the app to recognize the trigger phrase without causing false detections. Try raising the sensitivity by 5 units at a time.
If raising the sensitivity does not work, or if doing so causes too many false detections, try changing the trigger phrase itself. In general, longer phrases with more syllables reduce false detection.