Which model of Kia do you have?
So essentially its not downshifting?
You mention you've taken it back to the supplier so what have they done upto this point?
There are alot of inputs that that gearbox will likely need to see in order for it to work..ideally most of these checks need to be done diagnostically sadly to checks those with regards ***** ***** sensors plus ensuring the pedal switch does work..they also need to see if the valve body/plate performs as priamrily thats whats shifts the gearbox into gear...but normally the first ideal checks on problems like this is with regards ***** ***** fluid level aswell as loose fitting harness plugs to the gearbox control unit/valve block...there area few sensor on these boxes so they all baiscally need to be visually inspected..having said that if its new vehicle of 2016 then any problems that car ultimately has should be warranty covered...
With all due respect..you asked for advice or ideas as you requested above..you never mentioned anything that you already knew off unless you had equipment already to diagnose this? which i could of given steps to check further...you have to understand that we can only give advice based on the information and circumstances you provide and thats what was given above.any mechanic with half a brain would do these checks above..if it had failure of download software or updated software to the tcm..thats the dealers or technician who attempted to upload the software at fault and nobody else's..