If you are using UA miles for an award ticket from the US, it will only cover until the port of entry into SA (JNB) on a single award. You will need to book a separate award or ticket to go to Kruger/Cape Town. I don't think you can even fly straight thru from US to CPT on a single award ticket, unless your first stop is CTP. Not sure what your routing would be. That's is why nothing is coming up on the site.

UA call centers are still a mess, so I am not sure if you can get better information on the phone or not.

Hope this helps.