What can cause streamlines to be coincident with a face to which they should be normal?

I have an inlet that also serves as a particle seed face. However, when I run the simulation, the streamlines do not emanate from the inlet/seed face in a normal orientation. Instead of coming away from it, they look like they are embedded within the plane of the inlet/seed face. They do not extend beyond the edges of the inlet face. I have checked to make sure that the properties for the face deem it an inlet for which flow is "surface normal." (If it is relevant, the initial flow volume fluid velocity is zero along each simulation axis.)
What causes this?

Thanks in advance for your help.