The 3 MC Net Changes data file names are start with 'GLNBMC'. Interestingly, I see these 3 files in single currency sample data, likely created by the data conversion from GL 81A to GL 90A. Based on your comments, I suspect that the Retrieve Prior Year is looking for the existance of these data files and because the don't exist in the current year data, the problem message appears.

Is this preventing retrieval of the prior year, or just a warning when running the 'Integrity' check within the Retrieve Prior Year function? If just a warning, you should just be able to go ahead.

If you are prevented from importing, then it is possible that there was a data conversion problem at the beginning and the data was not properly converted. You could try copying in these data files from a different data set and rename the extension (since they won'y be used), but if you try this then do so on a copy of the data and perform a data integrity check.