Error: Duplicate name-value combination in variation specifics.

This means you have exactly the same variation combinations, like "Color:Red Size:XXL" and "Color:Red Size:XXL"

Solution:

Download the excel attachment of an Excel   Check duplicate variations.xls  .

Export your listing, especially the variations. Copy and paste the multi-variation combinations to the Excel to check duplicate variation. If it is duplicated, the yellow column will show you which rows are duplicated.