Hello everyone,
I’m glad to hear the positive reports that custom lobbies are fully functioning again. The issue would have been resolved following the maintenance that occurred earlier today.
Due to a large influx of players during the holiday break, one of the backend services for Starcraft 2 experienced an instability which caused these errors. This is why the service would function properly when there were less players attempting to play custom games (during off-peak hours), but the issue would return during the more popular hours of the day.
Thank you all for hanging in there and reporting the information that you were able to. Our Starcraft 2 team will aim to improve the response to issues like this going forward and will be working to improve stability to prevent it from reoccurring in the future.