[Screenshot_4] [Screenshot_5] [Screenshot_6] The Problem occurs on the Uno r4 WiFi and an ESP32 dev board. Connected via USB-c cable (works otherwise). Windows 11 latest version Reinstalled latest Arduino IDE Uno and ESP32 libraries installed nothing connected to the boards It has worked …

[image] siomo123: any tips Use USBDeview to see what happens when you connect your MCU board to the PC. Check whether a new USB device appears at all. View any installed/connected USB device on your system USBDeview is a software that lists all USB devices that connected to your…

You seem to be using 3 different COM ports in those screen shots, like you are not sure which is the correct one to use. It's easy to know which one to use. It's the one that appears when you plug the Arduino in and disappears when you unplug it. If no new port appears when you plug in the Arduino…

[image] PaulRB: using 3 different COM ports in those screen shots @siomo123 With USBDeview running, plug the board into the USB port and watch what changes: What happens Next step Nothing changes Investigate USB/Windows/cable/USB port as the common cause. A USB device appears, but…

Ok, sorry. I just didn't know how it was supposed to look like as it's been a while since I last used it. There was actually no indication of what port it's connected to and online guides just say one should try then out until one finds the correct one. How do i go about further hunting down the p…

[image] siomo123: How do i go about further hunting down the problem/ solving it? Please follow the steps in post #4 and tell us which of the three cases applies.

Hi @siomo123 . [image] siomo123: The Problem occurs on the Uno r4 WiFi and an ESP32 dev board. Let's start by focusing exclusively on solving the problem for the UNO R4 WiFi. If we instead try to troubleshoot both boards at the same time, we are likely to get confused and waste time. Once we …

Nothing changes, the L- LED doesn't even go on.

Hmmm. This is a bad sign. It means that either the bootloader on the board's Renesas RA4M1 microcontroller has been erased, or that the RA4M1 is in a state that causes it to not run the bootloader. Neither of these things will ever occur under normal operating conditions. It is possible a short o…

I checked for anything on the board: no debree, wire etc.. There was also nothing connected to it since the beginning of the troubleshooting.

Can't load any code on my boards

Official Hardware UNO Family UNO R4 WiFi

siomo123 August 10, 2026, 9:28pm 7

ok so it's case 2. The Uno is registered as ,,Unknown USB Device" and no COM is listed.

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Can't load any code on my boards

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