A new batch of tickets for the event went on sale today (March 25), but many were greeted with an "access denied" message on the BBC website, while others had to wait over an hour to get through to the sales page.
Ticketing company See Tickets explained that it had seen "high volumes of traffic" on its site, while Radio 1 said that it was "working hard to get this fixed as soon as possible".
Tickets are now sold-out for those who live outside Hackney, but more will become available at 4pm tomorrow (March 26) for people who have already registered.
Jay-Z and Rihanna will headline the weekend of June 23-24 at Hackney Marshes.
Rihanna will also headline this year's Wireless Festival at Hyde Park on July 8.
Example, Lana Del Rey, Florence + the Machine, Ed Sheeran and Leona Lewis are among the long-list of acts who will perform during the weekend.
The lineup for the event so far is as follows:
Bombay Bicycle Club
Chase & Status
Florence + The Machine
Flux Pavilion and Doctor P
Lana Del Rey
Swedish House Mafia
The Ting Tings