Just bring it online as soon as possible.
There is no “maintenance mode” and unlikely it would be implemented in the future:
Your node have 288 hours offline before it would be suspended, then you have a week to fix the issue, if after a week it would be still suspended - it will be disqualified.
To recover your node need to be online for the next 30 days. The node will be on review for the next 30 days after solving the offline issue, if the node will be suspended again at the end of 30 days review period - it will be disqualified.
So you have plenty of time to fix the offline issue before the node would be disqualified.