What Should I Do?

A partner at a VC fund shared my profile with a Founder-CEO (Series A / 90 People team). Founder-CEO got in touch via WhatsApp text hoping to get on an introductory call. We decided on a time and spoke the following weekend for 20 minutes. As a next step, we decided to catch-up in person. I visited his office on a Sunday at around 10:00am and then we left for lunch at around 3:00pm - finishing our meeting at around 6:00 pm. The conversation just flowed and both of us exchanged a lot of information in those 8 hours. Towards the end, I told the founder I am interested. And he asked for two days time to get back to me. He reverted back after 5 days on Friday evening where we spoke for another 20 minutes, and he asked about my intent and my compensation etc. - he said, he will get back to me the next day after an internal discussion with a final yes or no. We both agreed to speak around 3:00 PM the following day - Saturday. The following day, I left him a text saying "I look forward to speak at 3:00 PM etc. in the morning" to which he did not respond. And then he didn't call at 3:00 PM. Not leaving any text etc. I waited from Saturday until Tuesday morning and called his investor who introduced us. Investor asked me to call him fora final closure and if he doesn't revert then he will investigate. At this point, the Founder-CEO hasn't responded. What should I do? (I don't want the investor to follow up with him as that might trigger some phobia about my reach with his board member.)