I have an I30 SLX and on purchase I paid for an additional Fob KEY, that was programmed OK.
Since my wife had that second key all the time, I felt I should have a spare hidden in the car in case the original ones battery went flat. So I bought another from the agent (special low cost) !
However on the service departments attempt to activate it, their Hyundai computer station / program denied a 3rd key ! Apparently the program has this limit.
It was interesting that if a new Fob is programmed, then the 1st one plus the car must all be reset and saved in the program and at the same time all those funnies of options IE auto door locking etc, can be reviewed and initiated or deleted etc. All programming is done via patch lead plugged onto the key hole. There were some 20? options saved, a bit like saving a spreadsheet
So I kept the 3rd fob key, as although it won't remotely open doors, it still functions to start the car and could in the future be handy if one of the other keys is lost etc. However then I would have to submit both for a reprogramming session which costs only $33.
I did sit in on the resetting and saw it all happening and a very interesting occasion.
regards fro Dave