High Pass sharpening is lost when i add a layer mask

Hi - I use high pass sharpening.  Once  sharpened i add a layer mask, invert and then usually can just paint out the bits i want to reveal of the sharpened layer.  Nothing is happening in the mask and its driving me nuts.

Using overlay, everything at 100% but nothing reveals with the mask.  Even tried the reverse and leaving the layer sharp and painting out most of the sharp bits but that doesn't work either.

If i delete the layer mask the sharpened layer reveals itself again but if i add a mask and i switch the layer on and off the high pass sharpening disappears.

Basically when i add a mask the high pass sharpening cannot be altered.

What am i doing wrong?  I have been using high pass sharpening for years without any problems.

I totally uninstalled and reinstalled PS CC yesterday and the issue has not gone away?