I recently tried installing the AMC app on my UN65KS8000FXZA. I've never had any issues with apps until now. When I open the app it shows the loading screen for a few seconds, then I get a black screen with "problem with config request". I've reinstalled the app probably 17 times, checked and I'm on the latest firmware 1242, and reset the smart hub. Nothing has fixed it.
Since this is the only app that you are having issues with this seems to be an issue with AMC. I would recommend reaching out to their support form.
Is this the only app that you are having issues with? Also, have you tried a factory reset on the TV?
This is the only app I'm having problems with.
I haven't done a factory reset yet because I spent a lot of time tweaking the calibration and I don't want to lose that. I did however do a reset of the smart hub, but that didn't fix it.