Outdoor Camera Software Won't Update

I purchased and installed 3 additional outdoor cameras on July 15.  They spend a large part of the time in  "Offline" status.  All 3 have not updated their software since I received them.  They all have software version 1.15.6.391.  I've removed and re-added cameras multiple times.  I've reset the base station multiple times.  I feel like if the software would update to 1.18, like the rest of my cameras, they would stay online, like the rest of my cameras.  Why won't the software update?