Did you board originally boot into Android of Linux? There are two different boards you can buy:
- The AWS kit with Linux
- The Basic kit with Android
In general, plugging the board in with the power supply will boot the board up into which ever OS was originally installed onto the board. Add in the MicroUSB cable should not affect the booting; however, it will make limit the use of the USB Type-A ports on the board. i.e. you can only use either the type-A ports or the OTG, they are mutually exclusive and once you plug in the OTG port, the Type-A ports will not work.
I have not seen a board malfunction when both are plugged in, though some people do not expect the mutual exclusivity of the ports.
My suggestion is to re-flash the board with a new OS from the list found here: https://www.96boards.org/documentation/consumer/dragonboard410c/downloads/
Once you have re-flashed, and still have issues, we can explore the possibility of a hard brick. Right now, it sounds like it is only a soft brick.
Please feel free to join us on the #96Boards and #OpenHours IRC channels as well for more support
We are also available weekly during our live stream open forum on OpenHours