Issues with Video : PBS Help

The video I am trying to watch doesn't expire until much later, why am I getting a message that it's unavailable?
I am getting the message "This video is unavailable in your area." Why?
The video I'm watching is stalling or has choppy video playback.
The video I'm watching is only streaming audio, there is no video.
I am getting an error message saying that I'm outside the United States. Why?
I'm getting an error message saying the source file not available.
I am watching a video and it suddenly ends only 20 minutes in. Why?
I want to watch Downton Abbey live on my device but it's not available.
I can see an episode's clips or previews, but it says the full episode is unavailable for streaming. Why am I receiving this message?