Yes, I'm experiencing the very same problem and don't know how to resolve it. Prime video is totally black screen while audio works just fine. Netflix and others are fine too. Who do we contact, I wonder.
I got Prime to work! This might not work for you, but here goes:
So, the problem was that on Amazon Prime I was only getting audio and not video, right?
I was using composite video to feed the signal to the display, because I'm going through an older A/V mixer for good audio. Since the Roku that was still working in another room was set up on HDMI, I decided to try using HDMI direct to the display where I wasn't getting a Prime picture. That worked. The only problem is that when I set it back like it had been, with the video running composite, it still worked. I expected it not to, but it worked. At that point I decided to leave it set up with the HDMI, as it does have a better picture. If I actually use the VCR or the DVD player, I'll just have to set the display back to composite.
Thank you for your reply. I'm not sure what all that means what you did with yours, but we only have one TV and a computer/monitor, and the TV is an older model. I've unplugged and plugged it back up. I've deleted the app and restored it on ROKU. I have updated everything. I have changed the display back and forth from widescreen. I've turned ROKU off and back on again. And probably repeated it all with no change. It works fine on the computer, but it's still a blank screen on the TV.