You need to get in contact with the person who requested the demo, and with them identify all the stakeholders who contribute to the decision. Then you need to talk to all those stakeholders.

It's great that "you know" your product will make a big difference for them...problem is, THEY have to believe that, too.

So your job is to find out where they're at. Do they share this belief? Are they skeptical? Have they been burned before? What questions do they have?

These things all need to be uncovered BEFORE you do any sort of presentation.

Finally, a word about language. If a person or company isn't yet using your solution, and hasn't paid for it, they aren't a "client"...they're a prospect.

So right now you have a good prospect. Find out as much as you can about them and the situation they are in.