Watch the CRT as the machine boots. The BMDC should not count down to Zero. If it does, it is not loading correctly.
The other possibility is that the software is not meant for that version of the BMDC. There are a bunch of parameters that load and it all must match.
I am assuming the DOM and software may have come from EMI-inc.net.
The SX machine when new, booted from a floppy and used DOS 5.0.