I tried contacting support for one of the websites that was unavailable on BestChange website and I couldn't get a clear answer from their support.
Maybe they don't speak english language very well, but I asked them a clear question, so there is no reason to avoid answering me.
In most cases, the issue is connected with unavailability for our parser to access the file containing exchange rates the exchanger produces. There are many possible reasons for such situation to occur, but all of them lay upon the exchanger's or hosting's side (considering the fact that the other 400+ exchangers continue to display exchange rates correctly). In case our software is unable to correctly access the exchanger's website or to process the information produced, we do not display such data and set its status to "unavailable", although the website itself may remain accessible to users.