Hello. If you are using the model door of Cloud Materials, it cannot be opened;

If you are using a custom solid wood door, in 3D/Walkthrough, directly press the shortcut key O to open/close the door, or right-click on the wooden door - Door Leaf Switch - Open/Close/Custom Angle Open, and you can enter the required opening angle to open the customized door. The screenshots of the operation steps are as follows: