There wasn't a SDK or platform to build on and we didn't take any actual orders for anything (so we had minimal success stories or $$$). The hardware we showed was built by us, and ran a custom OS (not based on linux) that was nearly impossible to work with. We had a very talented engineer rage-quit after spending a week attempting to figure out how the OS handled the internal message bus system to debug an issue.

The hardware was also crazy expensive. We built literally everything: the vehicles, autopilot, the autopilot OS, the comms board that connected to motors (and enclosures), the sensor boards (GPS, gyro, etc), the radio that talked to the autopilot, the flight planning software, and later an entire enterprise cloud stack written in only the newest of the new JS frameworks and containers. The team often decided to do things such as not use off-the-shelf processors like the Nvidia TK1 or existing embedded software solutions -- nothing was 'good enough' so everything was invented.

Oh, and did I mention we also cycled through recruiters like candy?