To prepare for the upcoming update at the end of November (presumably version 1.9), Fire Emblem Heroes will be offline for maintenance between 14th November at 11 pm (UTC) and 15th November at 2 am (UTC).

For reference, the downtime ends 1 hour and 30 mins before the next scheduled Feh Channel broadcast starts. So, with luck, it won’t be long before we know what’s in the mysterious planned update!