Help Center now accesss Apple's servers, so if your Internet connection is slow or poor, you'll find that timeouts are causing your issues. As for the app, it may or may not have included it's help files inside its program. You'll need to check with them or identify the app, so others can comment. For Apple's new delivery system: File a bug report with Apple.
Unfortunately, though, your answer did not solve my problem. I clicked the button accidentally.
My internet connection is OK, it is a 6MBit DSL connection and quite reliable. So it is not that.
The app is “Sigma Photo Pro”. The Help Center says it has a help page but I cannot access it.
However, the Help Center app is always slow, no matter which help topic I am trying to access. The “currently not available” message appears for Apple apps as well. I have already tried deleting the cache files to no avail.
And regarding filing a bug report, what could I tell them? “Your app just doesn’t work” does not seem like a proper bug report.
But thanks anyway!