Beautiful place but here is some info so you have fewer surprises.
Venice has many bridges with many stairs. Hire a porter to take your luggage to and from the place if you have a lot. Favile has a recommendation.
If you arrive by train send one person to get the key and the others to stay at the train station with the luggage. As the key getter exits the station turn right and go over the modern bridge to Piazza Roma. The key box is very near, the closest building to the parking lot and to the left. Then return to the train station and take the stone bridge across the canal to get to the apartment This bridge is to the left as you exit the station.
If you have a lot of luggage hire a porter, there are many stairs.
Do not try to find the apartment with it's address. Search for Hotel Falier. The alley to the apartment is right next to it.
Hopefully the gate key mechanism will be fixed but if not you have to reach around to the back of the mechanism and insert the key in the back lock. It is easy once you know it has to be done.
Unless they change things be prepared for a kitchen that has none of the staples you may be used to seeing at other AirBnBs. No coffee, tea, salt, pepper, nothing like that. If you plan to cook simple meals be sure to bring everything you need or go shopping. There is a small store about 15 minutes away.
The place is really beautiful and has the best shower I have ever used ❤️!