Inverting a mask means masked regions become unmasked and unmasked regions become masked.
Edit > Invert layer does not affect Shape layers.
Select the mask layer you want to invert.
In the Canvas Layer Editor choose Edit > Invert layer or Edit > Invert Mask
If you select an image layer then choose Edit > Invert Mask, all masks linked to that layer are inverted.
Select the invisibility mask layer you want to invert.
In the Canvas Layer Editor choose Edit > Invert layer or Edit > Invert Invisibility mask.
If you select an image layer then choose Edit > Invert invisibility mask, all invisibility masks linked to that layer are inverted.