Damn, sales is hard … even when you have a really good product

Maybe try setting up a face-to-face meeting?

Try other channels. Are the potential customers on Twitter? LinkedIn? Do you have their mobile number so you can SMS? These channels are not overcrowded with sales messages yet. Formulate a VERY short but insightful message from their perspective, how your solution can help them in a concrete way - numbers, if possible. Then follow up by phone to suggest a meeting.

Create content so you get seen as an industry expert. Blog on your company site, or create your own. From there you will start to gain traction. This will take 6-12 months of consistently writing pieces, so it will not jive with "venture" timeframes.

Here's my observation: 99% of people are useless. They're very unprofessional and do the bare minimum to get by. Your goal is to the find the 1%. It's simply a sales funnel.

Find one person in the industry who's opinion matters. Actually find 20 of them. Focus on selling to these 20. The sale to one of these will push the sale through to the rest of the industry along the lines of "if so and so did it, we must too."

Sales is hard. Take an objective view point to your strategy the same way you would consider a sales reps approach, and apply the same critisicm to your own work. Also: have some brainstorming with marketing, get everyone together and be serious about driving goals, they will see you as someone you has drive and you'll all be on the same page.

You need to find a coach in the company you are trying to penetrate. Someone who knows the inside politics. This is usually not the ultimate decisions makers, but someone who can help you understand the culture of the company. Who makes decisions. What is the procurement process? It is much easier to find a coach than reaching the key players these days. Think about how your coach can benefit from helping you. Can you make the coach a hero for recommending you?

Also, if you are local to the company you are trying to penetrate find decision makers on the golf course. I once targeted the CEO of a major company and stalked him at a golf tournament. I stood beside him and opened the conversation with how great the tournament was for the local community and lead me booking an appointment with his CIO.

Best of luck!