Hi Darcy,
I use an Atomos Samurai recording DNxHD 220x and can use those files in Sony Movie Studio 13 Platinum. I have the same Avid codec installed LE 2.7.3.
I think you problem may be, having too many audio channels. My camera doesn’t feed audio via the SDI, so I connect my audio through the 2-channel stereo option. If you are recording the same way, Movie Studio should allow the DNxHD files. However, your error code implies there are too many audio channels for Movie Studio to handle.
I would perform a quick test sample video recording on the Ninja with just stereo audio. If that is working, you could run your videos through a converter problem to reduce the multi-channel audio to stereo. If you need all the multi-channels, I don’t think Movie Studio is capable of processing anything greater than stereo (2 channel). If that is the case you might want to consider that Vegas Pro should handle the additional channel audio (I would check that out before upgrading, because I’m not sure).
Hope this helps…..
Best Regards……George