This is with the latest daily build (2017-07-21 a27b6ae), also happened on earlier dailys (2017-06-24 or something) not tested with older builds. Might be a regression.
As soon as you add a texture to a particle simulation, the simulation no longer works.
Steps to reproduce:
- Create a plane, add a particle system, set it to hair
- Enable Hair Dynamics
- Add a Force Field (I used Wind blowing in Y direction)
- Hit Alt-A to play, the Hair bows in Y direction as expected
- On the particle system, add a texture, use a b/w image texture and set its influence to length+density
- Hit Alt-A again, the Hair no longer moves
This can be worked around by baking a setting without the texture, and afterwards adding the texture back in.
I can of course upload a sample project, but this bug is so easy to reproduce that I don't think that's necessary.
I hope this problem hasn't been submitted yet, I didn't find it if it has.