Issue with brush opacity on layer mask

In the past adding a mask on a layer (in this example on the layer with the city image), and then using the brush tool would reveal the bottom layer (in this example the red layer).

However, now the brush won't fully reveal the bottom (red) layer at 100%.  The city layer is still visible where the brush tool was applied. Am I missing something, or did Photoshop change something?

I have the brush set at normal/ 100% opacity.

Using Photoshop 23.1.0