- Fri Sep 11, 2020 5:48 am
You could have a conflict in the board manager. I've seen this happen with our ESP32 board definitions, which is part of the reason why we handed that of to Espressif. Essentially, the Arduino IDE couldn't handle multiple definitions of the same board (from SparkFun and Espressif) and even if the board definitions were installed, they might or might not show up in the list of boards. Often, this would occur for users with multiple versions of the Arduino IDE.
The only way I was able to easily resolve the issue was to uninstall the Arduino IDE and manually delete the folder containing the board definitions... aka go for a clean slate. It sounds like this could be a similar case.