S80 power windows failure after battery change

Sounds like the window regulator lost its settings after the battery change. Did you try resetting the window positions? Usually, you hold the window switch down until the window is fully open, then hold it down for a few more seconds. Repeat when closing the window, holding the switch up for a few seconds after it's fully closed. Does that work?

I tried holding the switch down and up after the window was fully open/closed, but nothing happened. Still completely dead. Is there maybe a specific sequence or something else I should be trying? Or could it be something more serious, like a faulty regulator?

If the manual reset isn't working and there's a fault code stored, it's likely the regulator needs to be properly initialized with diagnostic equipment. A generic OBD scanner might not be able to do it. Best bet is to take it to a workshop with Volvo-specific diagnostic tools. They can confirm the issue and properly initialize the regulators.

I took it to a workshop, and you were right, they had to use their computer to re-initialize the window regulators. Cost me 290€, but at least it's fixed! Appreciate the help!