Hi Bob,
Did you just download the new version of the Mosaic app, or did you also update your Rossini DAC as well?
If you have only downloaded the new version of the app, you’ll need to get the Rossini updated for this to work. This can be done by browsing to the IP address of the Rossini on a web browser (you can see details on how to determine the IP address of your Rossini here), clicking on Device Settings, then under the Internet Update section clicking Check for update. The unit should update correctly from there.
It is a good idea to power cycle your Rossini with the rear panel power rocker switch before commencing the update, just to help make sure everything goes smoothly.