Sorry, just to be clear. If you turn it on without touching
any buttons it is going to err0? Or only when you are turning it on with the "check OS" button combination?
If everything works as it should and the err0 is showing up after the os flashes on the screen, that has nothing to do with the error list in the manual and the unit is perfectly fine.
I guess I assumed that you already had an audio interface and a midi cable. I would think that the cable you linked would work but can't say for sure as I've never used it and I can't open the "read me" file from the mac update on my computer.
https://www.boss.info/us/support/by_pro ... s_drivers/I have one of these m-audio cables
https://www.thomann.de/gb/maudio_midisp ... r_274906_1and was going to try it out but there only seems to be a mac version for updating by midi.
If it is in Err0 right when you turn it on, unless you got it for hella cheap and don't mind spending a little bit of money on the cable, you might want to return it if this was not disclosed. You could also open it up and see if there are any broken solder joints around that 4mb ram chip.
Also, have you tried turning it on without the card in it?