I am having the same problem with my KS-2. I have followed the directions exactly. I downloaded the update. Unzipped the .bin file. Transferred it to a formatted SD card, in the root directory and inserted it in to the camera, held down the menu button and turned it on and the camera starts up as usual. I have 3 Pentaxes...the KS-2, K-70 and the K-3. They all need to be updated but I am having no success. Any other ideas?
---------- Post added 05-03-20 at 04:57 PM ----------
OK...I know this will shock you but it was user error on my part

so I have now successfully update all 3 of my cameras. I thought I was putting the .bin file in the root directory of the SD card but I was putting it into the DCIM folder.