I also have this issue. I’m in an area with good 3G/4G coverage. It seems to happen in the evenings for me. The option works well for me at other times of the day.
I’m getting the sense that Kia is running out of API calls for routing requests from their mapping provider, given the timing (i.e. end of the day).
It’s definitely not a connection issue, because I can see traffic data in my area where there are no HD Radio traffic info.
When does routing act up for you?