Unable to create vector mask always

Hi Everyone,

I am trying to learn how to create vector mask as part of a tutorial on how to add clothing patterns to clothing in photoshop but when I get to the step that is meant to convert to vector mask it does not work for me.

Would anybody have any suggestions what I can do please?

The following are the steps I used:

*Photo of white shirt

*Path selected up top and on right

*Used curvature pen tool and made a selection on a part of the shirt and closed the path

*double clicked to bring up name path box

*named the path then clicked ok

*clicked underneath the path (on right) to deselect the path on shirt

*dragged background to new layer icon to create background copy

*turn off background visibility

*held down control key and then clicked add layer mask icon

At this point it should become a vector mask with grid background and just the part of shirt I  have isolated with pen tool visible but for some reason it isn't always doing this for me.

The strange this is it sometimes works and sometimes doesn't!??

If i'm lucky it will show the grid, but other times when i press control and add layer mask it will not change the main picture on the screen and only adds another icon next to the background copy layer but even when i click the icon it still does nothing....

I have tried different things like hold down control key first and then press add layer mouse click, tried pressing both down together hard etc..but there seems to be nothing thst makes it work consistantly for me.