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 Nano" vs. "Arduino Nano Every" vs. "Arduino Nano IoT" vs "Arduino Nano 33 BLE" vs. "Arduino Nano RP2040 Connect".
Make sure you have selected the port of your Arduino board from the Arduino IDE's Tools > Port menu.
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.
Note that having the wrong selection in the Arduino IDE's Tools > Processor menu will cause this sort of error. So even if you fixed whatever was the cause of the original upload error, if you changed this setting in the meantime then you will be getting the error from a new cause.
So my recommendation is to try each upload for both the Tools > Processor > ATmega328P and Tools > Processor > ATmega328P (Old Bootloader) settings until you have fixed the problem.