Anything connected to pins 0 and 1? That can interfere with the upload.
If your Uno does not use the CH340 TTL-to-USB converter, you can run the loop-back test (Loop-Back Test Instructions)
Anything connected to pins 0 and 1? That can interfere with the upload.
If your Uno does not use the CH340 TTL-to-USB converter, you can run the loop-back test (Loop-Back Test Instructions)