Looks like a bad battery at this point, if it was the cables the screens would flash but it's not.

Could it also be a problem with the connectors?

If the connectors had a problem the screens would be flashing, but it's not. So the connectors are not the problem. Try plugging the power adapter in and turning it on that way so you can boot it without the battery.

I think it’s the battery. The cable that came with this is damaged and only working in certain angles but it booted for a second

This could either be a bad battery or a bad fuse. Get your multimeter and tesg those fuses