On several occasions (three to my certain knowledge) the following has happened:
1) App insists that there is no internet/data connection, with button to retry. this error message is repeated for the thirty or fourth attempts at retrying that I make.
2) At this point, I either go to Airplane mode, or swap from wifi to 3G. On turning off Airplane mode (or switching back to wifi), an iOS style 'Immortalis download complete' message/notification happens.
Given this is intermittent, and hasn't happened during a battle, thus is not critical, but may indicate some issue.