Don't really have a strong resume in setting up a DLNA server but I thought there might be value in taking a look at the OEM info that I found here:
http://www.sonore.us/SOtM1.htmlSTANDARD FEATURES
The SOtM Mini Server supports up to 24 bit playback at the following sample rates: 44.1KHz, 48KHz, 88.2KHz, 96KHz, 176.4KHz, 192KHz, 352.8KHz and 384KHz
The SOtM Mini Server plays AAC, AIFF, ALAC, FLAC, MP3, and WAV files from HTTP streams
So, the files you're trying to play are covered.
I also note that the Update Instructions were revised a few weeks ago, does that mean that a firmware update was released? And, most importantly, have you installed that firmware?
You're trying to use (by the webpage) Mode #3a:
Mode #3a - DLNA Output Mode
This mode is not yet documented in the manual. This mode utilizes streams from DLNA servers and controllers. Playback has been enhanced and now uses MPD as the renderer. With JRiver, BubbleUPNP and AudioNet as controllers this mode supports true gapless playback for FLAC, ALAC, WAV, and AIFF. DSD/DoP output is supported via USB if your server supports DoP streaming.
That implies to me that DLNA is a platform that is still under development. Further to the point, out of 5 possible modes, only 1 is reported to be documented (i.e. Squeezelite). What does SOtM say?
I can't find a forum or support page, so that I could look at the current manual. Personally, I'm concerned for you that SOtM doesn't appear to offer better support. For your problem, I suspect that they are the best party to resolve the issue. I say this because MC has a long development track record, so it probably is not the problem.
While the collective experience and knowledge that you'll find here may surely help, I'd expect that it would be more time efficient consulting the manufacturer of your equipment and ruling out problems there first. I would like to think I'm wrong.
In any case, I wish you all the best sorting your problem out.