DSD 256 not working on Melco with Accuphase

[mblssmp2]

I wonder if somebody can help me with this. I have recently bought an Accuphase DP-560 SACD player but I also have had a Melco N1 for a while. The DP-560 can also be used a DAC by connecting a computer to it. It is supposed to be able to play up to DSD 256 but when I connect the MELCO to it plays DSD 128 files but not DSD 256. I tried MinimServer and Twonky and with both server software, I get the problem. It is not a huge problem as I am only now using the Melco as a secondary source. I only have very few DSD 256 albums and in fact, I can download them as DSD 128 too. I just find it very off that I have this problem and I would like to understand it.