I am having trouble with layer mask settings (I THINK)

Hi there, this is my first post of hopefully many i love using photoshop however my enjoy has been mered wtih an issue i have with my layer mask..

When i try to use layer mask to blend two images together where it used to completely remove the top layer it now only removes like 80% leaving like transparent viewof the top layer????

I have tried all the settings i can find in mask to reset this. I have reset mask tool only and then even all tools.



Yup i sure have. they are set to 100%
and yet it still is there.....

Could it be the brush setting? when i use the brush to work on the mask its like its only removing 80%
Please forgive my ignorance but where do i find that out? or change it? are you talking in brush settings? or mask settings?