Serial Port not responding

I have a DUE that programs fine but the Serial Monitor will stop responding after a few commands (programming port). Serial.available turns into always false.

Now, I ran across this issue with programming port hardware:

And, I have the "bad" board type.

Is this likely the issue I have?

Just what is the fix? The article leaves some confusion about that. Would that be a 4k7 between pin 0 (RX) and 3.3?

Or is this something else?