The article covered that about half way down - the short version is that the Swedish authorities tried to interview him in London but Ecuador wouldn't let him be interviewed by the Swedish authorities unless Sweden agreed on a pre-condition that they couldn't lawfully agree to.

> In March 2015, however, the SPA changed its position and requested to interview Assange in London. A spokesperson for Assange welcomed the development and said Assange wanted to be interviewed.

> This was followed in June 2015 by a formal request to the English and Ecuadorean authorities.

> But the SPA were not able to proceed as Ecuador did not give the requisite permissions. The trip to London by a Swedish prosecutor had to be abandoned.