Thank you Chris, you really solved my problem. The orange knob trick worked on my KIA too.I have just had this problem, and saw a way to fix this on Youtube - do a search for Niro PHEV charging. The fix is to remove the chargeing cable and plug, open the bonnet and pull the orange knob that is used as an emergency release to unlock the plug. You need to pull this hard until you hear a loud click. This fix worked for me.
I think the issue is the lock that locks the plug sometimes gets stuck, and the electronics sees that the plug lock hasn't activated so won't initiate a charge - pulling on the manual release must get the lock working again. If this becomes a persistent problem then the plug locking mechanism needs to be replaced.
I had noticed when plugging in the charging plug, after a few seconds there is usually a large click as the green charge light comes on - the click being the plug lock activating. I noticed when this fault had happened that there was no click and after 15 seconds or so the red fault light would come on.
Here is the Youtube link: