not in sync

Hi, I've recently been unable to upload sketches to my Arduino Uno, previously it all worked fine. The error message says:

Uflash:w:C:/Users/David/AppData/Local/Temp/arduino-create-agent661972794/Heater_Bank_Control.hex:i avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x9d

and then tries 9 more times to get sync, but fails!

I don't know what "sync" this is, sync between what and what?, I've been through the troubleshooting guide and other questions on the forum but nothing seems to quite answer. I tried re-installing the software, using a different Arduino Uno, all to no avail.

I am using chrome on Windows 7. I'm not aware of any changes to my PC between the last time it worked and when uploading stopped working but to be sure I tried using a different PC, which didn't work either, I've also tried uploading a sketch that I know works, still no joy.

Can anyone help?

Thanks

@dlooser the easiest think would be to reset your board.

  • turn on Verbose Output in the Preferences panel
  • when you see Global variables use 184 bytes (8%) of dynamic memory, leaving 1864 bytes for local variables. Maximum is 2048 bytes. printed in the output area under the code press the reset button on the UNO

let us know if this solves the problem