@Dave227 I know you need the ad off of AirBnB, and you need it off fast.
That is why I am suggesting you go after the guests and the tenant.
Whenever I hear a story of a property owner battling with AirBnB to take a listing down, it always take a long, long time. And there isn't even much chance of success.
You said "I believe Airbnb have the responsibilty to asked for some sort of proof that the tenant have the authority to sublease."
AirBnB believes differently, and will fight you for a long, long time about that. They have all the time and money in the world to fight you on that point. That's why I don't suggest that strategy.
However, if, as I suggest, you stop the AirBnB guests from being able to check in, the guests will cancel. The tenant will stop receiving money, and will even be penalized monetarily. If you can stop the guests from being able to check in, then the *tenant* will take the AirBnb listing off because it will be costing him money. And the tenant can take the listing off instantly.
The moment you make the AirBnB listing unprofitable for the tenant, the tenant will take it down.
The fastest way to get the listing off is to make the tenant want the listing off.
The fastest way to make the tenant want the listing off is to stop the money.
Regarding the existing lockbox: take the lockbox off entirely. Get rid of it. Put up a sign that says "AirBnB is forbidden here. AirBnB guests are not welcome to stay. You are trespassing."
Hand the key to the tenant.
Why does your existing tenant need a lockbox? They have a key. They "live" there.
You are not preventing them from entering the unit at all.
Make sure the key is the kind you cannot copy.