With Reporting Snapshots, you might come across this error message.




When you click into the row, it shows you the list of fields that have not been mapped properly.

Solution:
Check your mappings and the data type between the source and target fields. If that still does not solve the issue, check that the RUNNING USER has access to the source and target fields.

In this case, the 'Admin User' did not have access to the source fields and hence this error message.