Alexa can't decipher follow-up audio from Band

I do believe that at least once in the past I was able to use my Band to unlock my front door and supply the code required for that function. At present, when I use the Alexa function to tell my Band to unlock my front door (August smart lock), the band does display a text asking for the lock’s code and appears to be waiting for an audio reply. No matter how clearly I enunciate, it doesn’t understand and doesn’t unlock my door. When I check the audio history on the website Alexa app, it says the audio could not be understood --except one time it actually got the last two numbers out of four in my code.

Any tips for making this work? Is it a timing issue where I just need to reply faster?