This is a new message beginning in 7.1. It results when all of the source records are mapped to Bypass because the system is no longer generating summary rows for those mapped to Bypass. The workaround is to set the Is Optional Data Load workflow setting to True which allows the user to complete their workflow when the import fails, without needing to complete the Import-Validate-Load steps. Another workaround would be to change your transformation rules to map the data to a dummy member you could create outside of your reporting hierarchies.
Hello, I encountered the same message. Thanks for the answer, the second workaround worked, it disappeared after I mapped the members in the One to One mapping. I am unsure that changing the property Is Optional Data Load to True helped much in my case. I realized afterward that I had a Bypass rule bypassing all the rows of the set of data.