Fill not working

Recently, my "Fill" stopped working. I use the lasso tool to select something I'd like to eithere fill in or replace and then right-click inside the selection. I then select "fill" and after clicking to initiate the fix, nothing happens. The dialogue box disappears as if to suggest it has worked. The selection lines are still there. But nothing has been changed.

I tried resetting the tool to default. No change. I don't think it's about using the wrong layer because I use mostly use Lightroom Classic and go to Photoshop for repair work ... and more importantly, I only work on the initial background copy layer.

Any thoughts why this is happening? Have I unwittingly checked a box or changed a setting that influences this?

Im using a Macbook Pro, OS 13.6.6 (Ventura).