New Arduino Nano ESP32 (as of feb 2025), goes into an hung state shortly after loading a program. Symptoms are that the board's LED flashes blue red green, does not read or print, and will not load a new program. This started with a complex program, so I back off to using blink. I set a long blink time (delay 5000) to make sure I could see it work or not, and it did not work. I tried reloading the sketch and got this error message: "dfu-util: No DFU capable USB device available Failed uploading: uploading error: exit status 74", the light continues to show rainbow blink. After a little reading I was able to determine that pressing the reset button a couple of times, quickly, would reset the board so that it shows green on the LED. At which point I can load successfully again. However, that gets me back into the hung state. What do the rainbow lights mean, and how can I get the board working again?
Have you looked at the NANO esp32 hardware documentation at Arduino.cc Hardware or maybe Documentation?
Short update. Did the reset (twice, quickly) then powered the board off. Plugged the USB cable back in and blink sketch loads and works. So, I've not framed the problem well enough. Will look into this more; back to the more complex code perhaps.
Ah yes. After I submitted (Sigh): more ignorant now, but learning.
Don't blame yourself, that board is a bit different.
Shortly after last reply, my board went into a completely hung state. Any example program, including the empty sketch, loaded but resulted in the rainbow cycle in the title of this post. Despair descended and I cogitated for a few days.
The solution was to put the board into "bootloader mode" and install the sketch+loader (i.e. open the Sketch menu and select Upload Using Programmer). Then unplugged USB cable and reconnected it. After that all sketches loading and working as expected (even the !Serial flag).
Happy camper. The wood stove is cooking!