Cannot upload programs to Arduino Uno

I have two Arduino Uno Boards and I cannot upload any sketches to them. Both of these boards were, and appear to still be, working. I have uploaded sketches to both of them in the past and they still run the sketches that they last had uploaded to them but I cannot upload any new sketch, including Blink. The on-line IDE gets as far as saying BUSY but never uploads the sketch.

I have tried the following. Uploading from three different computers. Three different USB cables. Two different Arduino Uno boards. Many computer reboots.

Any ideas of how to solve or troubleshoot this problem would be greatly appreciated.

Thank you.

There is currently a known issue with uploading in the Arduino Web Editor: If you want to get notifications of any progress in fixing this issue, please visit the link above and then click the "Receive Emails" button. Someone will update that thread as there is any news on the situation, but we can't do the same for all the many other threads about this issue.

Until then, you can use the standard Arduino IDE. You can download it for free from this page:

I had this problem all weekend, and I had to re-install Arduino. My sketch uploaded with the desktop software only.

We released a new version of Create Agent that should fix this issue. You can check if you have it by clicking on the icon in the traybar and see that it says "Agent Version 1.1.86-5c199c1".

If by any change your Create Agent doesn't update itself, uninstall and reinstall it.

If you still have problems with this new version please let us know.

Quick note to all affected.

You may have to temporarily disable you antivirus or similar and maybe even install as Administrator. There might be a false positive on some antivirus.