The camera won.t turn on the battery charger blinks red when trying to charge both of my battreies

I had the same problem with flashing red light on my charging dock (within 10 sec after 2nd green light came on). I did fix it. There is a rust brown securing tab that holds the battery in place. Mine must have a broken spring..... So, I put the battery into my camera, pushed securing tab over the battery and then wedged a toothpick tip to keep battery tab in place. Once back on the charger, I had no more flashing red light. The battery is charging correctly. The problem was that the battery was not held down into place correctly. I now just have to unwedge the toothpick tip to remove the battery...but not really an issue at all as I keep the battery in there all the time. Very easy fix!!!
Others suggested to reseat the plastic dock. But mine was secure. Somewhere there is not a good battery connection that is causing the red flashing light. I am thankful to figure it out. Hope this helps you.