If there is an item placed in the four squares in front of the door to the player's Home, this will block the door. The door being blocked by the item will prevent the player from accessing their Home, as they must get to the door to go into the house.
Below is an example of a door that has been blocked by an object a player has placed.
By removing the item or moving it to a different location, the player will then be able to enter their house.
For more information on a player's Home, please see the following article: