Why won't my battery charge when plugged into a knockoff AC adapter?

"3rd-party adapters might not have the same efficiency as the original charger, and their QC is usually much worse.

However, if you can use the notebook - I suspect the case is the former - the adapter is not supplying enough power (because of its non-efficiency) to power the notebook and charge the battery at the same time. It's one or the other.

Shutdown your notebook - see if the battery charges."

Sounds like the knockoff AC adapter isn't meeting their own specs. If this is the case, can you return it as defective?

Contacts become worn, bent and dirty over time. I would suggest trying to clean the power connector port with contact cleaner. Since it is female, there wouldn't be much you could do on the male side except bend it ever so slightly to force contact. I've heard (though not proven) that this can occur with laptop battery connectors also. IMO, connectors on computers in general are pretty flimsy.