get a battery buzzer and see if its the wires in the battery,
https://hobbyking.com/en_us/8s-battery-capacity-meter.html?queryID=814d372bf5bff278a76caa03fe43ac65&objectID=73791&indexName=hbk_live_products_analytics
id say the balance wires are not connected to battery or the small connector on end aren't making contact . look at connections. try a non balanced charge not sure if that charger can do that?