Recently I changed the region of by Samsung UE40JU6400K on "Setup" menú to gain access to some new Apps on SmartHUB that I can't install on my country. Since then, the App Amazon Prime Video shows a black screen but sound on most of videos. Before changing the country I didn't have any similar problem... even some series I watched some days ago now It doesn't work.
I'm pretty sure that it's any kind of problem with codecs caused when I changed the region. So I came back to my normal region/country and I tried to restore the TV to factory settings, to restore the SmartHub, etc. but I still have the same problem.
I'm using firmware version 1550 and as far as I can see it's complicated (and risk) to make downgrade.