We've (Inkling) been in business for 4.5 years, and this is par for the course. Interest can start hot, then it tapers off, then it might pick up again extremely hot 18 months from now. This happens all the time with large companies who are constantly trying to make plans with thousands of different people. Budgets change, priorities change. The only constant is that things change.
This is why you can't fear sending the occasional ping to the person. I think you can figure out best the frequency of such a ping. But if you just had a meeting 2 weeks ago, it doesn't sound too interruptive to send a casual email or phone call that you want to follow up on the things you think you can help with.
Keep persisting, but just keep in mind not to persist to being annoying. Just keep it short and simple. A couple sentences is perfect. Is there something new you've thought about in the last couple weeks you could mention that a meeting would be perfect for, or a link to something educational that your prospective client could get a lot of use from?
I just blogged about this last week, but repetition is a skill too many people avoid because they think they've already said it, they don't have to or shouldn't say it again.
If you look at studies like this one Nielsen did with Facebook:
"Taking the look at organic impressions one step further, recall, awareness and purchase intent were still rising after 10 or more exposures to the message. These results stand in strong contrast to the scant four impressions that usually influence growth in these dimensions for standard display campaigns. What’s more, the jump in awareness between the consumers who were exposed to between three and nine organic messages and those were exposed to 10 or more was a considerable 15 points."
Awareness about a brand jumped from 13% to 28% when someone was exposed to a message 10 or more times on Facebook.
Sometimes people just need a reminder and another reminder and another reminder that you exist.
Just ask yourself how often you'd want someone to reach out to you to see if they can help you.