Troubleshooting

The tools do nothing when I press their keys

The Image Editor must show an image, and the mouse must be over it. Hotkeys don't fire in UV mode. In Mask mode, Blender's own mask keys win: switch back to View.

The panel says the selection is out of date

The image under a wand selection changed. Click Re-evaluate to redo your clicks on the new pixels, or turn on Auto Re-evaluate.

Select Object or Behind Objects does nothing

Click Enable Passes, then render once. Both read passes from the last render.

My layers don't show in the final render

CS Layers must sit between Render Layers and your Composite or File Output. Insert After puts it after the active node; check the compositor tree.

A layer's image went missing

The panel flags a moved file. Relink it with Blender's File ▸ External Data ▸ Find Missing Files.