F22 Simpilot said:
So you're referring to the radio? Not just some USB plug found in the car? That would be the difference in what the issue could be.

Try another USB stick is another option. SanDisk, Kingston or something that's really brand name.
There is a USB A socket in front of the gear selector connected to the infotainment system for playback of music files and infotainment software updates. I've tried various Kia approved USB sticks. The USB drives and files have no errors so the problem is the socket, car cabling or possibly a software bug in the infotainment system.