Are you sure you flashed the firmware correctly? For example, OpenSprinkler 2.0 and 2.1 uses different microcontroller frequencies. If you flashed the firmware code under the wrong board profile, the microcontorller will not start. You can always use the firmware updater program to reflash the microcontroller to one of the pre-compiled firmwares.
If this doesn’t solve the problem, please email [email protected] to arrange for support. Thank you.