Instead of punishing him to get his attention, try to acknowledge his mood as if his character was behaving like himself in-game. For example, if the party is fighting orcs, you can attack him with one of the orcs, miss on purpose and describe the scene using an element of his background, such as:

"The orc bearing the axe charges towards you. You easily deflect his first blow, they are really clumsy. It reminded you of that night at that giant's lair on the spine of the world, where you could see the giant's blows coming for hours before they hit. You could dodge them with a blindfold. A pity there was only copper and rotten meat in his loot, what a waste of time, at least the cave provided a decent shelter for the cold night, despite the reek and... The image of the orc's blade approaching your eyes takes you back to the present and you arch yourself backwards on a split second, and thus dodging the blow. You can feel the woosh of his blade right near your nose. While dodging the blow, you glance up the ceiling and you see one of their shamans trying to hide in an alcove on the ceiling while casting some sort of spell".

So, by doing this, you acknowledged his feelings, accepted it as part of the game as if he was roleplaying, and added a new element to the encounter that now depends on him taking a decision. He is the only one who knows the shaman is casting a spell upstairs. Having your feelings acknowledged is a powerful psychological tool for engagement.

I'm against granting circumstantial bonuses just to get them back to the game, as it would make the power play kind of player expect those bonuses and use manta-game to plan their actions around it. I would advise against anything greater then a one-time advantage on a roll.

Instead of punishing him to get his attention, try to acknowledge his mood as if his character was behaving like himself in-game. For example, if the party is fighting orcs, you can attack him with one of the orcs, miss on purpose and describe the scene using an element of his background, such as:

The orc bearing the axe charges towards you. You easily deflect his first blow, they are really clumsy. It reminded you of that night at that giant's lair on the spine of the world, where you could see the giant's blows coming for hours before they hit. You could dodge them with a blindfold. A pity there was only copper and rotten meat in his loot, what a waste of time, at least the cave provided a decent shelter for the cold night, despite the reek and... The image of the orc's blade approaching your eyes takes you back to the present and you arch yourself backwards on a split second, and thus dodging the blow. You can feel the woosh of his blade right near your nose. While dodging the blow, you glance up the ceiling and you see one of their shamans trying to hide in an alcove on the ceiling while casting some sort of spell.

So, by doing this, you acknowledged his feelings, accepted it as part of the game as if he was roleplaying, and added a new element to the encounter that now depends on him taking a decision. He is the only one who knows the shaman is casting a spell upstairs. Having your feelings acknowledged is a powerful psychological tool for engagement.

I'm against granting circumstantial bonuses just to get them back to the game, as it would make the power play kind of player expect those bonuses and use manta-game to plan their actions around it. I would advise against anything greater then a one-time advantage on a roll.