My camera says it’s offline

My camera was working fine till one die the battery discharged. So I got the battery and I put it to charge several times over the course of a month and when I would put the battery back into the camera the camera would shine a rainbowish light at the bottom of the camera the whole time the battery was in. So recently I bought a new battery and I’m charging it right now. If the battery isn’t the problem then what is and how do I fix it. Can I fix it. Because Ive had the camera for about 7 months before this happened.