Remove any connections to pins 0 and 1 on your Arduino board. These pins are used for communication with your computer, including uploads. Connecting anything to these pins can interfere with uploads.
Make sure you have the correct board selected from the Arduino IDE's Tools > Board menu. Note that some boards have similar names, but are not interchangeable. Examples include "Arduino Uno" vs. "Arduino Uno WiFi" vs. "Arduino Uno WiFi Rev2", "Arduino Nano" vs. "Arduino Nano Every" vs. "Arduino Nano IoT" vs "Arduino Nano 33 BLE" vs. "Arduino Nano RP2040 Connect", "Arduino Duemilanove" vs. "Arduino Due".
Make sure you have selected the port of your Arduino board from the Arduino IDE's Tools > Port menu.
Sometimes the port will be labeled with the board name in the menu. Other times it will not. If you don’t know which port is your Arduino board, you can find it like this:
- Unplug your Arduino board from the computer.
- Select Tools > Port from the Arduino IDE's menus.
- Note the ports, if any, listed in the menu.
- Close the Tools menu. The ports list is only updated when the Tools menu is re-opened, so this step is essential.
- Plug your Arduino board into the computer.
- Select Tools > Port from the Arduino IDE's menus. - The new port listed in the menu is your Arduino board.