Battery Works, Vacuum Not Charging

I purchased the SMOROBOT Tank X11 Cordless Robotic Pool Cleaner and it worked great over the first few months of purchase. However, I am now having an issue with it charging.

I have plugged the charging cord/battery unit into a number of outlets around my home and they all make the light on the battery unit glow green as it should to show there is power being produced. But once I plug the battery charger into my X11 Pool Cleaner, the light on the battery charger itself changes from green to red. Additionally, the charging light indicators on the vacuum itself never come on.

Because of this issue I am no longer able to use the vacuum nor clean my pool - very frustrating. Some assistance on this issue would be helpful. Thanks.