Why can't I get the checkered pattern?

SRenee  wrote I don't want any tutorials at this stage please.

Having looked at the other threads where you have asked very similar questions , it suggests that you do need to follow some tutorials.

For your immediate question with the selection made, click on the mask and Edit >Fill then fill with black. That will make your selected area transparent.

Dave

Delete the exisiting layer mask first,

when you make the selection, hold Down Alt key + click on the layer mask icon in the layer panel ( the square with a black circle), this will mask the selected Area,

if you did not press the Alt key it will make the opposite,

anyway, to invert the Mask:

click on the mask thumbnail and press ctrl + i