PBS not working on Apple TV. Other channels are fine
I have similar issues.  All works fine on the Apple TV with the exception of streaming the PBS shows.  PBS works fine on my PC.  I'm using an Apple TV2 and have a Passport subscription to PBS. We just finished watching Victoria and other Masterpiece series a while back but now, after the commercials play, I get 'Error loading Content' or Content not available now, try again later'.

You and I will need to work with PBS support to fix out accounts in all likelihood.