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That may mean there is no dial tone sensed by the telephones.
Do you hear one when you lift any receiver? if all are dead-silent, presumably your phone service has gone out during the night.
Do you have any alternate phone, e.g. cell phone or internet phone, to call the phone provider? (If your phone provider is from a box in your home, e.g. Ooma, Comcast, Verizon VoIP, let me know, and I will advise you further as appropriate.)
Calling the phone service provider is advisable at this point.