Translation:If the enemy is not cooperative, then you need to use the device.
Not from just that information, I'm afraid.
In general, Duo is supposed to ignore commas and full stops.
What might help is a screenshot -- the next time your answer is rejected merely because of a difference in punctuation, could you make a screenshot and upload it somewhere (e.g. an image-sharing host), then post the URL to the image in the appropriate sentence discussion?
First check that you got all the letters right (e.g. I [eye] versus l [ell]; all apostrophes; etc.).