The Danforth anchor needs to be placed quite a bit forward of the pivot point, so the weight will take it over. Plow and claw anchors have shorter arms, and still need to pivot rearward but not as far. In the pic I'm pointing out where the balance point is, which is also the pivot point. Also show about where the pivot should be.
Could add some weight to the far end
Here are a couple guides which also pivot more to the rear.
Delta
Claw or Bruce
