Flamestrike
Legend
So, your Hide check, while invisible auto-succeeds since you are Heavily Obscured and all checks that rely on sight automatically fail?
We've covered this. There is no Hide check. You're not rolling to 'no longer be seen' with the Hide action.
In order to take the Hide action you first need to make yourself unable to be seen clearly. If you are able to be seen clearly, you cannot take the Hide action.
Being 'unseen' is the prerequisite to attempting the Hide action.
Example:
Its the start of your turn in combat. You are playing a Monk (Stealth +8, movement 50') and you are currently standing in the open in a large warehouse with large crates scattered about the place, the nearest one about 15' away from you to your left, and another 20' behind you. Your friends are fighting a bunch of Orcs 30' away from you towards the centre of the room.
You have 1 HP left, and no Ki points and you have decided you want your PC to hide and wait the combat out.
At the moment you cannot Hide because the Orcs are able to see you clearly (you're in the open 30' away from them).
So you move 20' to the crate behind you. and duck behind it. You now have total cover relative to the Orcs, but are not yet hidden.
However now you can attempt to hide (as an Action) because the Orcs can no longer see you clearly. You use the Hide action, and roll Stealth, rolling a 14 and scoring a 22 - easily enough to beat the Orcs Passive perception score. You are now hidden, and will remain hidden until you either reveal yourself or the Orcs locate you with the Search action, rolling a 22 or higher on their Perception checks (your Stealth result).
If you were invisible at the start of your turn, you would not have had to move behind the crate to hide. You could have simply Hidden (via the Hide action) and (if successful) snuck off with your 50' movement, slinking away invisible and hidden.