Look in the Particle System settings for the Icosphere. Near the bottom is a section named “Field Weights.” The Turbulence slider is turned down to zero. Try increasing it.
That will get it working, but here are a couple of other things to be aware of: the falloff for the field itself is set to 5.4, which is a fairly fast falloff for the effect strength. You might try a lower number, say 2. And then finally, the particle dynamics are being saved to a disk cache. Be aware that sometimes if you change a setting and don’t see the particles react differently, you might want to “free” your cache to get Blender to recalculate the dynamics.