Cannot Place Door Needs Support

I was experiencing this issue, and I discovered that the issue appears when I have a different floor than the default wooden floor. What I do is change the floor to the default wooden floor by pressing R then T and I select the default wooden floor. I switch to the door placement option, and I select the door I wish to install into the doorway. Place the door switch back to the modification screen by pressing tab select the floor Press R then T and change to whichever floor you wish to use.