2560 Can't upload sketches anymore.?

I am having problems with my mega 2560. My programmer says it is assigned to port 4 but it is not communicating with the 2560. I have moved the cord from one usb port to another . it makes no difference. the programmer thinks it is communicating but the 2560 has a old program in it and just keeps running it. I have tried rebooting the programmer (the arduino software programmer) and the computer. I cannot get the two to find each other. What am I doing wrong?

Please don’t HIJACK other threads especially if it is not the same issue or arduino.

Could you please read this before using the forum in future.

Bob.

Programmer? Is it breadboard not Arduino?
I think, we need more detailed information.