Right. What you've got there is empty 16-bit code, and a 64-bit system won't run 16-bit code (I probably shouldn't have said "dos" - won't run any 16-bit code... I don't know what else it would be...). If it worked several months ago, that's a mystery!
I would again suggest "dosbox", or write 32- or 64-bit code like the message says...
Best,
Frank