If for whatever reason that the internet connection on your device is offline then the data will not be to upload on that given day, however, the data will still be stored and every day missed will be uploaded at the point the connection is restored.
In terms of reporting, in the event of no internet connection, Proof of Play "Additional Data" reports can still be produced as planned, which cover a period the Player has not uploaded the logs for. When the Player can once again connect to our server the missed data will be added as an "Additional Data" report and cannot be attached with the original main report.