Saturday saw the first official anniversary event for Pokémon Go. The augmented reality title took the world by storm when it arrived last year, attracting millions of players and plenty of complaints. To mark the occasion, developer Niantic held a festival at Chicago’s Grant Park on Saturday, but things didn’t go too well.

Around 20,000 fans turned up for Pokémon Go Fest. Excitement was high, with some attendees reportedly having paid up to $400 online for tickets. They were told to expect rare Pokémon appearances around the park, team challenges, and special medals and rewards.

Unfortunately for those in attendance, spotty cellular reception and server problems resulted in people being denied the chance to play the game for most of the day, with many unable to even log in. The server issues were worldwide, meaning it affected other events, including one in the UK.

Some of the gathered crowd turned their anger toward those who appeared on stage. Boos, shouts of “fix the game,” and chants of “we can’t play” greeted pretty much everyone who addressed the audience.

Niantic’s Chief Marketing Officer, Mike Quigley, tried to calm the situation by announcing that everyone in attendance would receive the first Legendary Pokemon – Lugia - in their accounts. Niantic has also offered ticket refunds, $100 of in-game Pokécoins, and more.

Despite the technical problems and long queues, some at the event said they enjoyed the opportunity to mix with other Pokémon Go fans. Assuming there will be more festivals, expect Niantic to make sure things run smoother in the future.