Sony laptop red cross appearing over the battery


I have been experiencing an issue with my laptop with a red cross appearing over the battery. This continued for a month until my laptop completely shut down and never came back on two weeks ago. I purchased a compatible battery online and received it today, after which I installed it and began charging the laptop. The red light in the front of the laptop confirms it is charging but it still isn't powering on! What is wrong with my laptop? Please help... thank you.