Maintenance and jail
Two things every operator eventually needs: taking the node down on purpose without being punished for it, and getting back out when it was punished anyway. Both live in the Node state card on your validator's page.
Planned maintenance
A validator that stops producing blocks gets slashed for downtime. Maintenance mode is how you tell the chain the silence is deliberate, so you can upgrade, move the machine or replace a disk without paying for it.
Enter maintenance parks the validator. Exit maintenance puts it back to work.
Sign it with the consensus key
Maintenance is the one thing in the panel sent from the consensus wallet, not the operator wallet. Connect the wallet your node signs blocks with, and the page tells you which address it is expecting if you have the wrong one connected.
Before you press it
The chain limits how many validators may be in maintenance at once, and the panel shows the count as slots in use. When the limit is reached you have to wait for somebody else to come back.
The button is also unavailable when too few validators would be left producing blocks, or when this validator has already used its maintenance turn for the period. The page says so rather than letting you send a transaction that reverts.
A validator that is not in the current validator set has nothing to park, and the panel says that too.
While you are in it
The card shows the block you entered at. Do the work, and then come back and press Exit maintenance.
Do not overstay. The chain forgives the missed blocks of a maintenance window, but only up to a point: staying in longer than allowed means the missed blocks are charged against you when you leave, scaled by the maintainSlashScale parameter. Maintenance is a window, not a pause button.
The honest way to use it: know what you are going to do before you enter, do it, and leave. If a job turns out to be longer than you thought, coming back and going in again later is safer than staying parked.
Getting out of jail
A validator is jailed when it is punished, for downtime or for a felony. While jailed it produces nothing, earns nothing and its delegators earn nothing.
Coming back is not automatic. Somebody has to release it, and two conditions have to be true first.
The jail time has to have passed. The panel shows when that is, counted from the punishment. Downtime and a felony carry very different jail terms.
The self delegation has to be back at the minimum. A slash takes stake out of the operator's own self delegation first, which can leave it below the required floor. If it is short, the panel says how much is needed, and the fix is to delegate more from the operator wallet before trying again.
Anyone may do it
Releasing a jailed validator is not restricted to its operator. Any connected wallet can press the button once the two conditions are met, which means a delegator who wants their stake earning again does not have to wait for the operator to wake up.
It is one transaction and it costs the sender gas. It changes nothing else and it gives the sender no claim on the validator.
After the release
The validator is eligible again. It returns to the active set when its stake puts it in the elected validators, the same as any other, so a validator that was slashed heavily may come back out of jail and still not be elected.
The order of things going wrong
Worth understanding before it happens, because the response is different at each step.
Missing a few blocks costs you the rewards for those blocks and nothing else.
Missing enough blocks crosses the misdemeanor threshold, and your pending rewards are redistributed.
Missing a lot of blocks crosses the felony threshold: stake is cut, and you are jailed.
Signing two conflicting blocks skips all of that. It is the serious offence, it carries a much larger slash and a much longer jail term, and it is usually caused by running two nodes on the same consensus key. See Run a node.
The exact thresholds and amounts are parameters governance sets, and they are listed with their current values in What governance can change.
What none of this can do
Maintenance does not protect you from a double sign. It parks a validator that is behaving; it does not excuse one that is signing conflicting blocks from two machines.
And nothing here reverses a slash. Coins that were cut are gone, to the system reward pot and to whoever reported it. The buttons on this page get you back to work; they do not get you back your stake.