The “Windows 10 IoT MSDN Support Forum” is probably a better place to discuss Windows 10 IoT since there aren’t very many Win10 users and devlopers hanging out here. You’ll be likely to attract more eyeballs on the Microsoft site because there is a bigger community of Windows 10 IoT users hanging out there:
PS I’m afraid I can’t help all that much although this does sound like eitehr the Dragonboard hasn’t entered the hardware download mode correctly or that the host is not able to connect. Make sure there is nothing attached to your DB410C except for the power cord and the micro USB type B cable (in particular make sure there is nothing connected the USB type A sockets). Note also that if you have a random type B charging cable be aware some of the very cheap ones (for charging headphones and the like) sometimes don’t include the data lines so also worth trying a different cable.