2 of my cameras stopped working at the same time?

I have 6 battery operated security cameras. They have worked flawlessly this passed year.I think ring did a great job.Today I check my cameras and 2 showing dead batteries at once. I go to my charging station and get the spares that I rotate so to always have the cameras on. I put fully charged batteries in the cameras showing dead batteries and cannot get either on to power up.Too much of a coincidence for 2 of my cameras to do thisat the same time.How can I resolve this ? Did you guys do a software update?We're my camera's hacked?Looking for suggestions.Thanks.