It would help to know what controller you are using? Not clear on what you mean by “software update”? Is it a centurion V? Or has it been updated to a Centurion 6 or 7 or a hard drive added? Does your machine have a floppy drive?
On my old Partner 1 with a Centurion V, if I try what you’re doing my machine tries to read the floppy drive. If the drive is empty I’ll get the 302 error. If you have it connected to a network and it sounds like you do, make sure the path to your .ncc files is correct. My machine is not connected to any network, so I can’t help you there.