Shimano STEPS E8000 battery won't charge
It looks like you might have bypassed the charge controller on the pack and charged the cells directly? The smarter pack controllers do a form of coulomb counting and will see anomalous or unexpected pack voltages as a risk and premptively brick. 

But before you get to that conclusion, I’d measure the individual cell voltages and make sure they are all within 0.1 volts of each other and that none are anomalously low. Balances often have a limited capacity for rebalancing and will brick a pack that is unbalanced too far. 

Finally if you want to repair the pack, you may find a new / used pack controller part on eBay or you might be able to scavenge off an older pack. But be aware some controllers do brick themselves at end of life so you might be SOL anyway. 

The worst case scenario is that you bricked the controller on the  pack and you can’t recover the controller. It’s not a huge loss. You can still break the pack apart and use the 18650 cells in other projects or sell them on eBay.