avrdude: stk500_recv(): programmer is not responding


I've received two Arduino Nanos today. They're both MEGA328P-based and have a CH340G usb chip. I'm using the same cable to connect them to my Mac. When I plugin the one Arduino Nano, I can flash it without any problems. When I try to flash the other Arduino Nano, I get the error "avrdude: stk500_recv(): programmer is not responding". Therefore, I guess that it's not a problem with the drivers on my Mac.
The "faulty" Nano has the L-Led blinking every second, so I guess that it also comes preloaded with a bootloader.
Any ideas what I might be missing here?


They both have the CH340 on them? Did both blink with the blink sketch?

They both have CH340 on them.
The one was blinking, the faulty one not (because I wasn't able to upload any programs onto it). The faulty one just has the L-led blinking repeatedly, but this is not a program that I have uploaded.

Could it be the blink sketch? (The one normally loaded at the factory).

Could be. But why am I not able to upload any programs at all to the "faulty" Nano, despite the two being practically identical.

I have no idea, (or at least not yet).

The reason I asked about the flashing LED is that if it does that it probably has a boot loader loaded which would rule that out as an issue.

Load the blink sketch on the good one and compare them. If they both run the same then do the loopback test on the non working board.