服务器自午夜起因维护而停机。

The server has been ___down for maintenance since midnight.

我无法提交报告，因为内部系统宕机了。

I couldn't submit my report because the internal system was ___down.

支付门户网站明天将因计划升级而暂停服务。

The payment portal will be ___down for a scheduled upgrade tomorrow.