Cold War with 120hz?

Hi! I recently bought the Xbox Series S. I've only ever played with 60hz until now. Would like to play with 120hz now. The thing is, as soon as I set 120hz in the settings, my monitor goes black and then I'm back in the menu where I set it. Only that it is then not at 120hz but still at 60. Is it maybe because of my monitor? Got the BenQ ZowieXl2411P PC Edition (144hz). Hopefully you can help me.

Could be your Xbox. If it doesn't deliver 120 Hz, the monitor can't do anything.

But she can