Painting on a layer mask doesn't work

[Simon617 0]

I have installed 1.7 but straight away I have hit an issue - With just the background pixel layer I add a brightness and contrast adjustment layer, I then highlight the adjustment in the layers panel and select a brush to paint out the effect using the paintbrush set to black and nothing happens. I have tried it on the last beta version an it works. This also used to work on 1.6 which has been overwritten 

I have reinstalled 1.7 from a fresh download but the same thing happens!

Windows 10 Version 1809 

[MEB 7,261]

Hi Simon617,
Welcome to Affinity Forums
Check if you have Protect Alpha ticked in the context toolbar for the Paint Brush Tool. Untick it if that's the case. The Opacity and Flow can also have the same effect - make sure they are not set to 0%.

[Simon617 0]

Just now, MEB said:

Hi Simon617,
Welcome to Affinity Forums
Check if you have Protect Alpha ticked in the context toolbar for the Paint Brush Tool. Untick it if that's the case.

OK Rookie mistake, yes I had that ticked it now works