According to Sony, that machine can only use AAC-LC DRM-Free format.
As you haven't given us the full encoding information of the file you are trying to play, the only assumption we can make is that is isn't that format & must be converted in order that the machine can play it.
File info after comments…
Information for File: 1hr Beta Binaural Beat Session (20hz) ~ Pure (256kbit).m4a General / Container Stream # 1 Total Audio Streams for this File -> 1 Audio Codecs Used -> AAC LC File Format -> MPEG-4 Play Time -> 1h 0mn Total File Size -> 109 MiB Total Stream BitRate -> 255 Kbps Encoded with -> Lavf56.4.101 Audio Stream # 1 Codec -> AAC Codec (FourCC) -> 40 Audio Stream Length -> 1h 0mn 0s 45ms Audio Stream BitRate -> 254 Kbps Audio Stream BitRate Mode -> CBR Number of Audio Channels -> 2 Audio Channel's Positions -> L R Sampling Rate -> 44.1 KHz Bit Depth -> 16 bits Audio Stream Size -> 109 MiB (99%) Which only leaves me with…
You'll have to ask Sony why it can't play that, as all indications are that it ought to be able to