Unable to boot with no terminal attached

[mahesh]

I installed the latest version of Ubuntu on a stick PC (Atom x5-Z8350, 4 GB memory), and although it's a puny little guy, Ubuntu runs nicely for what I intend to do with it. The problem I'm having is that if I do not have a monitor attached, Ubuntu will not boot. I can disconnect the keyboard and it will boot fine, but if the monitor is not connected to the stick PC's HDMI port, Ubuntu will not boot. I've tried both Ubuntu desktop and server, and the problem is the same with both. Kind of surprising, since I assumed that a server really doesn't need a monitor, but in my case, it clearly does. I don't think it's a BIOS issue since the stick PC used to run Windows 10 Pro in a remote configuration, and booted and ran just fine with no attached monitor or keyboard, and there's nothing in the BIOS that relates to keyboard or monitor connectivity.

So, any ideas of what I can look for or change to get this thing to boot in a headless more. I've looked at the boot log that failed and can't find anything, but I have no clue what to look for. I uploaded the log file of the failed boot to this Dropbox folder, if anyone wants to take a look at it. The end goal is to have this PC running headless as a network monitor, and I'm hoping that I can use Ubuntu to do this. It runs fine with a monitor attached, but that's not my goal.

Thanks in advance for any help or advice,