Glastonbury organisers are re-opening registration for tickets today at 1600 after the event did not sell out in the first two days.
Michael Eavis said on Monday that slow ticket sales were due to terrible weather in previous years, not the choice of main headliner Jay-Z.
100,000 had sold by Sunday afternoon out of a total of 137,500.
Organiser Emily Eavis says they are giving people who wanted to go another chance to register.
She said: "We're having a massive influx of people saying they didn't register.
"So what we're going to reopen registration and allow the extra people who want to come to do so."
The festival takes place at Worthy Farm in Somerset from 27-29 June and is being headlined by The Verve, rapper Jay-Z and Kings of Leon.
Emily Eavis says there are not that many tickets left and registration will remain open indefinitely.
She said: "We had registration open for a month and we're just going to reopen it.
"To be honest, there aren't that many tickets left to sell. They'll probably trickle along I imagine over the next few weeks. There won't be a massive surge."
To register you will need to submit basic personal details and a passport quality photo.
Once your application has been accepted you will be sent a confirmation email with a link allowing you to buy tickets immediately.
Emily Eavis says she is not sure what went wrong with the registration system.
She said: "All we can gauge it by is what the public's reaction is.
"What we're getting this end from people is that they want a chance to buy a ticket but they haven't got registration numbers."
Other acts playing at the festival include Hot Chip, British Sea Power, The Futureheads and music legends Leonard Cohen and Neil Diamond.
The rest of the line-up will be announced on 1 May.