Where can I get a replacement USb cable for a Harmony 880 remote in Sydney Australia?

HI. So there are a counple of things you will have to ensure for the connectivity to be successful.

1. You are not connected to the internet via a router
2. You are not on a wireless network
3. Any firewalls on your computer are disabled
4. Your USB cable and port are good, and the remote is not connected to a USB hub but right into the compter.

Now, please do the following:

1. Uninstall the software
2. Download it again at http://logitech.com/myharmony
3. Install
4. In your computer's add/remove programs, uninstall the Logitech Desktop Messenger
5. Take out the battery, press and hold the "OFF" button, and re-insert it. The remote will display "Safe Mode"
6. Connect your remote and log in to your account
7. Click "Downloads" at the top and select "Firmware". The firmware on the remote will update.
8. Click "Replace Remote" to conduct a connectivity check.
9. Update the remote.

That should get the remote working. :)

You can download the harmony program from there website. connect your remote with a USB cable to your computer and run the program. It's fairly easy to reprogram it.

If you have changed your hardware setup, you must reprogram your Harmony 880 using the Logitech software. You should be able to simply step through the 'interview-like' process and enter the new make and model number of the new hardware. It is usually recommended to add the new device first and then associate the new device with your existing Activities. Once your Activities have been mapped to use the new device, you can delete the old one. Once everything has been completed in the software, update your remote through the USB connection. Hope this helped!

First, check your battery indicator (make sure it's fully charged).  Second, dock your remote with the USB cable and reprogram the remote.  It's possible you disconnected before the programming was properly transmitted to your remote.  Finally, if things don't work, use the HELP button on the remote.  It should talk you through a procedure to fix your problem.