Fortnite is back online after almost three hours of downtime.
The video game was taken online to enable developer Epic Games to add new content to the title to commemorate the first anniversary of its launch worldwide.
Fortnite v5.1 includes a swathe of new limited time missions, as well as a new in-game weaponry, skins and content for players to unlock.
The video game went offline a little after 9am BST (4am ET), with Epic Games announcing the scheduled downtime had ended an hour later.
However, thousand of fans were still unable to access the successful title, which is currently available on Sony PS4, Windows PC, Xbox One, iOS and Nintendo Switch.
As the issues persisted, Fortnite acknowledged the difficulties by tweeting from its official account: 'We are aware of some players unable to access Birthday Challenges, they are currently being deployed to everyone!'
As of 12:15pm BST (7:15am ET) the issues appear to be resolved.
Fortnite first launched on July 25 2017, with the latest update marking a year since its initial release date. As a result, the birthday cake distributed throughout the game after the latest update has a large number '1' candle on its top.
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Fortnite was taken offline as it developers install an update to commemorate the first anniversary of the game. Fortnite v5.1 is being readied by the game's developers, Epic Games, and it will bring with it limited time missions as well as a new weapon, skins and content
The latest Fortnite birthday celebrations will run until August 7 and includes additions to both the Save the World mode and the Battle Royale option, Epic Games has confirmed.
The celebrations will see the reintroduction of 'Playground Mode' after its initial roll-out was hampered by worldwide glitches last month.
Elsewhere, the developers state that players will find 'celebratory birthday rewards' throughout the game for the next two weeks.
To unlock these rewards, players should play 14 matches to unlock 5,000 XP, dance at different birthday cakes across the in-game map, and deal 1,000 damage to opponents, which will unlock a new 'Fortnite Birthday' emoticon.
By completing all the challenges, players will earn the 'Birthday Cake Black Bling'.
On the official Epic Games website, it claims: 'Starting July 24th, we'll be celebrating #Fortnite1st with a limited time in-game event! You can earn special birthday cosmetics by completing birthday challenges and quests in-game.
'From the birthday Battle Bus to the sploder husks carrying a tasty surprise, we can't wait to party with you! The in-game celebration lasts until August 7!'
WHAT IS FORTNITE? THE FREE TO PLAY GAME LAUNCHED IN 2017 AND HAS TAKEN THE WORLD BY STORM
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Fortnite is a game that originally launched as a disk back in July 2017 and was then turned into a free-to-download game by its developer, Epic Games, in September.
There are three forms of the game: 'Battle Royale', 'Save The World' and 'Playground'.
Save the world is the original form of the game and is currently not available to play as part of the free-to-download game, instead it comes as part of a £30 ($40) extra.
It is a co-op mode with a story that's playable solo or online with friends.
Fortnite is a battle royale-style survival shooter where players create a superhero avatar and compete against each other on a dystopian island
Users compete in teams of up to three to complete a variety of missions.
It is rumoured that the game will be added to the free-to-play version of the game in the future.
Whilst Save The World may be the original version of the game, its sister mode is by far the most popular.
Battle Royale is a game of survival where players create a superhero avatar and compete against each other on a dystopian island.
Each game, or 'match' as each competition is known, starts with 100 players.
The aim of the game is to be the last one standing. Users can form allegiances and play in small groups.
To enable this and the interactive experience, the game allows completely open communication between players.
Inspired by the Hunger Games novels and films, gamers search for weapons to help them survive.
Armed with quirky weapons and amusing dances, the game has swept across the gaming world, with children flocking to it.
While there is no exact figure on how many children play Fortnite, the game has so far pulled in an audience of over 125 million players.
Playground is the latest addition to the game and is a consequence free mode with more loot and unlimited respawning to allow players to get creative.
It involved groups of up to four people working as a team and the players can hone their skills as the practise in advance of entering Battle Royale where they will face better players.
The update will also see the reintroduction of Playground mode after its stumbling introduction last month where it crashed almost instantly after launching
The update will also see the introduction of a gun that has been in demand for some time among Fortnite's devoted fans. The Compact SMG will be the newest weapon in Battle Royal and it will allow players to engage in close quarters combat with the high capacity, fast firing weapon
The latest update also sees the introduction of a new weapon for players to use in-game, known as the Compact SMG.
This new gun is the latest addition to Fortnite Battle Royal and will allow players to engage in close quarters combat with the high capacity, fast firing weapon.
Fortnite is a hugely popular game, amassing more than 125 million players in the year it has been in existence.
It is one of the most financially successful games in recent memory.
The celebration will run until August 7 and includes additions to both the Save the World mode and the Battle Royale option
Fortnite is introducing a special in-game questline tha involves unlocking Birthday Brigade Ramirez (pictured, right)). Finding and eating birthday cakes earn event tickets which can be spent on the limited time Birthday Llama (left)
Fortnite is available on Sony PS4, Windows PC, Xbox One, iOS and Nintendo Switch and will be launched on Android later this summer.
In the 90 days after launching on iOS, the developer behind the hugely-successful title pocketed £72 million ($100 million).
The survival shooter quickly climbed the ranks of the top 10 free iOS apps following its launch on the platform, beating the likes of Snapchat, Facebook and WhatsApp.
Fortnite was also the most downloaded app on iPad in the weeks after its release.
The game costs nothing to download and play, but does offer a plethora of in-app purchases. These include skins, dance moves and accessories.
The most expensive in-app item is £99.99 ($130).