That's because any bigger fillet - in radius - will eliminate some parts of your model...
You can deselect "Tangent propagation", and begin selecting manually. Try on one end of the chain and if that doesn't work, try the other end. Sometimes you actually have to have "tangent propagation" deselected and then manually select all of the edges.
Sometimes a fillet just won't take no matter what you do. I like to make a copy of the body or surface and then start to trim off sections trying to see if the fillet will take. For example, if the fillet just won't propagate down an edge, you can make a copy of the body, create a plane in an area fore or aft of where you thing the fillet is hanging up, use that plane to cut one side of one body, see if you can fillet (usually you can), then use the plane to cut of the other side of the other body and then create the fillet on the other body. Then you can combine the two bodies back together and you have a complete fillet. This method is a last resort method, but certainly have proven to be effective in my dealings with complex geometries.
Because i don't have your part file, the way I interpret from your image is that this can have propogation issue. The edge is visible of extruder boss. So fillet cannot know how to propogate between 2 faces. If you add part file then might be helpful.