This is an error being returned from Amazon that may appear when trying to send contents electronically. The error reads: 

Error InternalFailure We encountered an internal error. Please try again.

One possible cause that a user could easily troubleshoot is an unusual box dimension. Check the dimensions of each of the boxes in the shipment by selecting the shipment and Bulk Box Update from the bottom menu.

Then check each box for an unusual dimension (an error). If one is found, correct it and save the changes, then re-send contents. 

If that is NOT found to be the cause of the error, please contact support for further assistance.