Edge mask won't work on EEVEE render engine, Make sure your using cycles render engine.

Apply rotation and scale transformation for the object

to apply rotation and scale transformation  select the object then (Ctrl + A) and select Rotation & Scale from the apply menu

when new version released remove the current version by following these step

1. In Blender, navigate to Edit -> Preferences. Then the Addons tab.

2. Search for MaskNode and expand it

3. click the remove button

now install the new version by following these steps

1. In Blender, navigate to Edit -> Preferences. Then the Addons tab.

2. Hit the install button, locate the MaskNode new version zip and install the zip file.

3. Make sure the addon is displayed in the list and enabled

MaskNode's custom group will not appear when searched in add menu (Shift+A), Alternatively your can use 'F3' to search masks

Make sure 'Use Node' checkbox is checked