Mega2560: timeout communicating with programmer CURA

I know this thread is somewhat antique by now, but I was stumbling about the very same problem today - and did not find the solution for my case (neither here, nor elsewere). As this thread was somewhere at the top google results, here is just another point one might want to check:

Make sure no other programm is accessing your printer. In particular: Quit CURA, as it will block the communication.

It is also covered in a thousand more places such as this.

Please do not NECRO post.
Maybe a read of This may also help.