When in doubt, RTFM, which I did for the UK version. I wish I was more familiar with Hyundai, and I will be, but not yet as I don't have my Ioniq yet. Anyway, this seems to be a common issue across many Hyundai models.
There should be a small pinhole size reset button that you can use a ballpoint pen or a paper clip with just to the right of the Power/Volume button. Push that in, hold it for a few seconds just for good measure and try again. You will probably lose your radio presets and whatnot by doing that.
Another alternative is to pull the fuse for the multimedia unit and put it back in. While doing that, ensure the fuse is not blown and in good shape and replace if necessary.
Another bit in the manual says:
Select the [SETUP] button on the
audio system ➟ Select [System].
• Memory information: View My
Music memory usage.
• Language: Change the user language.
• Default: Reset the audio system.
Hope this helps!