I have that exact cable put together by Michigan Synth Works.
Maybe I missed this elsewhere, but I found that the I2C address for the 16n is 0x34 (per the firmware repo) so made that change in the disting MIDI/I2C set settings (I2C Address 52 0x34). (EDIT: This is bad info per desolationjones instruction)
I thought this discovery combined with the right combination of pull up switches would get me there. Not quite. Still zeros in history.
I did connect to the editor and confirmed midi works as well. So, the unit is A-OK, just something not connecting yet on I2C.