I can confirm this issue. If the Mosaic app updates itself to 1.2.0 (129) but the dCS device is still running 1.1.3 (506) - the previous version - the app will not see the dCS device. This means that the dCS device will need to be updated via a web browser to function correctly.
As noted above, this can be done by browsing to the IP address of the dCS unit on a web browser (you can see details on how to determine the IP address of your dCS unit here), clicking on Device Settings, then under the Internet Update section clicking Check for update. The unit should update correctly from there.
We are working to resolve this by way of a new app version ASAP. No further updates to the dCS unit will be required, just a new app version pushed to iOS / Android. This issue is not present if both the app and device are on the latest version, so once it has been updated everything will work correctly.
Apologies for the inconvenience here.