You may see this eBay error mixed in with other various eBay errors. 9/10 times, this is the actual error that needs to be fixed.
It means the variation names or variation values for the eBay listing in Listing Mirror do NOT match what eBay has.
This issue has two resolutions!
You can use the end and relist function to delete the listing on the marketplace, and re-push the listing in Listing Mirror out to eBay. This will force the marketplace to match what Listing Mirror has.
You can use the delete and reimport action to delete the listing in Listing Mirror, and import the eBay marketplace listing into Listing Mirror. This will force Listing Mirror to match what the marketplace has.