When a validator node is jailed, its operator must wait until the jail time has expired (see the jailing section of the FAQ for details on that) before sending an unjail transaction to the chain. To send an unjail transaction, do the following:
Run the bandd keys list command to get the address: value of your jailed node. Save the address by copying it, then typing ADDRESS=, then pasting the address. Then hit enter.
Next, send an unjail transaction to the network using the following command: