Found this on the KIA Owners UK Facebook page from a guy who works for KIA
For anyone with no clock display, information directly from Kia as I work for them, and have carried out this procedure today successfully. Press the reset button on the front of the stereo, it’s on the front near the screen a hole small enough to fit a cocktail stick in. Remove the audio fuse, and the SD card and leave for 15-20 minutes. Refit the fuse and SD card, and turn the audio system back on and allow it time to reboot. This should bring everything back to life. If you are not technically minded enough to do that, or if the above procedure doesn’t work then contact your Kia dealer.
I've put a copy of this post in the How To Guides forum - hope you don't mind - GTOldie
We can confirm we’ve received a small number of reports from our customers that the clock facility has stopped working on their navigation system.
Having investigated reports, we’ve identified this is due to an internal calendar issue affecting the clock display. To overcome this, a hard reset needs to be completed. This involves the fuse and battery being removed for more than 15 minutes.
The procedure should be done at a Kia dealer to ensure the unit reboots correctly. This will also allow them to take next steps if there is any resulting issue. All dealers have been made aware of this procedure (to be covered by warranty) so please give your dealer a call to arrange a booking.
If you’re unsure of your dealer’s details, you can find them using the following link: