The battery may or may not be fully dead. If a laptop battery hasn't been charged in a long time, cell voltage can drop below the threshold that the battery management electronics inside the battery requires, and it will refuse to charge. If the cells are not trash, you may be able to revive the battery by briefly applying voltage to the cells bypassing the protection circuit. However, you may need a special tool to convince the protection circuitry to unlock the battery, even when the cells are fine, again.
Typically, reviving a laptop battery will require to get access to the leads that go to the cells. Check out this video by Sorin for an example of how it can be done:
There is a shorter video by him where he just pokes two holes in the foil of the battery to get access but for the life of me, I can't find it right now.
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Phil