Looking at the door and clicking should work.
Try holding the hammer and clicking. If it does nothing, do ctrl+o, go to controls, find where it says fire, and change the key that it's set to by double-clicking it.
Wrench the door and make sure raycasting is on. A little check should be in the box next to it. If there is none, click the box to make a check, and click send.
Try clicking it then.
If it still does not work, wrench the door and make sure the event onactivate>self>door>toggle exists. This is done by wrenching the door and clicking events at the bottom of the pop-up window. If it is not, simply replace that door.
If the door is JVS, JVS is really glitchy and this is no surprise for me. Try using the default doors.
If all else fails, open console by pressing ~, type in "trace(1);" (no "), try clicking the door, and then open up console again and type in "trace(0);".
Then post console.log. Console.log is found in the Blockland folder, usually in Documents/Blockland. It's right in that folder, not in add-ons or anything else.
