Hey there Stardust747!
Thanks for bringing your question to the Apple Support Communities. It's always important to use external hard drives as a backup means for your computer. Though this specific error may lead us over to LaCie support, we can confirm that your iMac is able to recognize or "See" the device.
Confirm if your iMac is actually seeing the connected device by using System Profiler. Additionally, you may be interested in updating to the new El Capitan 10.11.6. This update resolves an issue that prevented some network devices, such as speakers and multifunction printers, from accessing SMB share points.
OS X: About System Information and System Profiler
Update the software on your Mac
If the LaCie Cloudbox is still not connecting, you may wish to confirm with LaCie support for additional troubleshooting.
Happy computing!