Neato XV-21 and lithium battery

I recently purchased this amazon.com/gp/product/B00N9IV64O but my XV-21 is giving me Battery issue 0002 error. It seems the battery is disconnected. With the lithium battery installed, the XV-21 doesn’t even turn on if it’s not docked.
Anybody knows how to solve it? This XV-21 is an older model which doesn’t have a on-off switch.