Yes. In Front View, Cameras are clicked 'on'.In the front view, under the "Show" menu make sure, "cameras" is ticked on.
We may be getting close. Today, as I was tackling the problem anew, I saw, in wireframe, a miniscule green line. I zoomed in, but it did not resemble a camera. However; the Outliner/Hypergraph said it was. I enlarged it with the Scale Tool & the attached pic. is what I got. (The line vertical to the plane is what I was seeing.) I had been scaling my cameras up in order that (after moving them about) I could see at a glance which way they were pointing. I don't know if this contributed to the problem. I'm also attaching the doc.Have you selected the camera in the outliner then selected the front view window and pressed the f key to frame the object? It could also possibly be outside the front views clipping planes.