I can't upload my program to Arduino Uno
Checks:


Check if the board has power (probably it will).
Check if the board is shown at the ports in the IDE (i.e. COM3: Arduino Uno).
Check if you put the correct board in the IDE (e.g. Uno, Mega etc.).
Check if you have multiple versions of the IDE running.
Check if you have multiple IDEs installed.
Check if you don't have the RX pin used while uploading a sketch.


Try the following:


Use a different USB port on your computer
Use a different USB cable
Reinstall the Arduino IDE