Insurance coverage denied owe $53,000

Has this happened to anyone? My insurance coverage was denied by my previous employer. I was working there when I had my baby and had full coverage. I was denied coverage of my baby girl because I did not call the Benefits center to let he know she was born. I called my office and My insurance but was not told to call the Benefits Center. What do I do?!? I didn't even make $53,000 when I worked there.