Hello & Welcome to Just Answer,
I'm Greg and will do my best to assist you today.
Sorry I didn't see your question earlier and to hear of any issue you are having with your phones.
If you have the FULL manual for this system, you will find the details about using the "Do Not Disturb" mode in the section about "Using Special Features".
For you convenience, I have ENLARGE that small section and attached it as an image here. NOTE: You MAY have to click on the attachment NAME - to see the image. I have also HIGHLIGHTED the specific steps to EXIT DND mode.
Please give these instructions a look, and let me know if you can exit DND mode.
Thanks, ***** *****