If there is nothing to settle, this is what the report will say. Confirm that the merchant actually has a settlement to batch.  You can do this by trying to run a current batch report 

Dejavoo: Daily Report / Detail Report on Current Batch
 or by trying to Reprint a receipt (Use LAST).
Dejavoo: Reprint receipt

 If there is a receipt to print, there is a batch to close

If there is a settle that needs to be batched, the error can be triggered by a connectivity issue. Run through troubleshooting steps to make sure the terminal is properly connected to the network.

Check the batch number to make sure that it is less than 999

Dejavoo: RB- U Error/Reset batch/unknown error

If the Settlement continues to Fail, If tidal Chat Tidal (During Business Hours) Before contacting TSYS for assistance