3820005 - Error in Logs: "Too many concurrent requests for ClientCode=TN"

I was searching for flights, car and a hotel and selected all of them to book.  When my trip returned in SAP Concur, I only saw the car and hotel booked.  The flights were not in the reservation.  I checked my trip and can see in the trip history that flight segments were booked.  I checked with my Travel Management Company (TMC) and they do not see the flights were booked. 

I see this error in the logs: Too many concurrent requests for ClientCode=TN

What is the cause of this and how can it be rectified?

Flight booking fails with 'Too many concurrent requests' error when booking flights, car, and hotel together. , KBA , CON-CA-ADM , Administration , Problem