Updated at 2:45 p.m.: Arena is back up and running.

Hearthstone is having a problem today.

Publisher Blizzard has confirmed that it is aware of problems that some players are running into when trying to play Arena games in the collectible-card battler Hearthstone: Heroes of Warcraft. It says it’s looking into the problems, and this led the company to bring the Arena offline for everyone. This comes just days before Blizzard plans to launch the latest add-on for the game, Blackrock Mountain.

We’ve asked the publisher for a comment further explaining the situation.

Earlier today, Blizzard released the latest patch for Hearthstone. This update included some fixes, and it also prepares the game for the Blackrock Mountain content.

This outage is only affecting the Arena, which is the mode that enables players to piece together a temporary deck in an attempt to take on up to 12 different human opponents before losing three times. The longer you go, the bigger the reward you get. It is an especially popular style of play for people who stream the game on video sites like Twitch.

Solo play and online ranked and casual games are all still working.