Multibuy has been temporarily disabled (http://community.eveonline.com/news/news-channels/eve-online-news/multibuy-has-been-disabled/)
29 September 2015, 1:24 pm
Hello players
Due to an issue we have discovered with the market system, we have disabled the new Multibuy functionality while we investigate further.
We will update you as we find out more.
Source: EVE Online News