How to fix a broken fairy lights

Hello,

I have a fariylight string which was working with a solar panel, however it stopped working suddenly, I don't know why, I opened it, and there is a battery that gets charged and then is used to supply the lights,

now what I want to do is, remove the solar panel and directly connect the lights to the battery,

I tried that, now I have two wires from the light, I connect either of them to the battery but it won't work, I used a tiny resistor from another device but it won't work too.

I watched a video where I can connect the two wires to a usb but it didn't work too.

I don't know if there's something wrong in the way I do it. I don't know if there is a positive wire and negative one but I've tried both and it won't work.

what should I do? and know that I've got no experience at all in electronics but I'm trying to.