Tried booking a roundtrip ticket - outbound UA and return TK, and was told that the fares are not combinable and that United can't book TK flights. HU. Notice the flight even though there's no price and wasn't ticketed was saved under my reservations and has a confirmation #. HUACA. This time I am told it's not ticketable because 1) the TK flight doesn't exist (not true in fact they fly this route multiple times a day). 2) Not combinable. 3) UA can't book TK over the water?

Anyone able to explain to me what actually happened?