Sensors stop communicating to the base station

I have 7 door and window Gen 1 and 2 sensors that were working fine for over a year. Here recently they have stopped working. They show open or offline.  I have a Gen 1 range extender also.  The battery charges are good.  I have 4 security cameras and doorbell camera that work fine. I have not made any changes.  Has their been a firmware update that is causing this?