3820734 - Why am I getting an error message "Unknown error trying to store fare" while booking multiple airlines (married connections)?

Users are trying to book a Fare that is returned in SAP Concur by combining American airlines and United Airlines but After selecting reserve and continue, they receive an error message as "Unknown error trying to store fare"

Users trying to book Multiple Airlines getting an error message in the reserve and continue Page as "Unknown error trying to store fare" , KBA , CON-CA-ADM , Administration , CON-CA , Cross Applications , CON-SRV-TRV-ADM-LAN , View Airlines , Problem