This is actually a known issue: https://codeberg.org/rimu/pyfedi/issues/1018

The basic takeaway is that you must have already enabled notifications by clicking the enable button that shows up in that box. Then, since they are enabled, the button doesn’t show up any more, so there is just an empty box left. To disable notification, you need to do that through your browser. It’s on the list to make this UI a bit clearer at some point.

Edit: This is what it looks like if you don’t have notifications enabled