Many people spend time on what they think are opportunities, but in fact they are not. I did it even myself when I started selling mobile machine translation solutions to handset manufactorers and mobile operators. The so-called managers wanted always to meet us, but there were clear red lights, they never made key decisions.
If you see red lights, or fyou feel them, go and find another potential client. Even when you see yellow lights, such as the key person not going to your meeting, you have two options, either you go faster, but you might crash, or you brake a bit and rethink the whole story.
If you can turn on the green light before you run out of gas, go ahead, otherwise, there might be better opportunities to spend your time on.