Can't charge my sp. New battery, new cord.

I've had this gameboy since it came out some where along the line it got put in storage and I lost it. After finding it I could Still turn it on and hear that jingle. I bought a. We shell and replaced it. I bought a new chord. When I plugged it in the light towards the bottom turned red and stayed red even when I turned it on. The screen made no attempt to start up. I read online it was mostly a dead battery and I'd need a new one well that new battery came today. And the same thing happened

I have no idea what to do. Is it spare parts? Did I mess something simple up changing the shell? Please help