When animating anchor points, I can't see the motion path. I have tried selecting the keyframes.
When opening the view options, the motion path is checked, and when opening the edit - preferences - display, I got "All keyframes" checked under motion path.
Where is it?
Anchor points only reveal their path in the layer view - just the same like point effects controls. Kinda logical, given that those coordinates are relative to the layer, not the comp or the 3D world space. The normal comp view will only show the layer's actual motion path.
Select it at the "View" popup at the bottom of the layer viewer (which in your case is hidden due to your interface layout).