Hi ingrid.
I'm sorry if I'm repeating what has already been said. Just trying to figure out what's going on with your game.
While the game is running, hold down Ctrl and Shift. While holding them down, press the C key. Your game will pause and the screen will slightly darken. At this point, you just start typing and it should show up in the upper left corner. You type in "testingcheatsenabled true" exactly like that, but without the quote marks. Then you press Enter. Now the game will start running normally again and it won't be dark. You can use the testing cheats at this point, such as Shift-clicking the mail box to get special options, or Shift-clicking your Sim to take him back to CAS. You can also turn on Buydebug once you've turned on testing cheats. To do this, you repeat the Shift-Ctrl-C sequence. The screen will darken and your game will pause. Type "buydebug" exactly like that without the quotes. Press Enter. Now Buydebug is operating and when you go to Buy Mode, you will see a question mark when you sort by function. The question mark will be right above the button for Comfort furniture.
Again, I'm sorry if this is all just repeat information. I wanted to spell out the entire process from start to finish to make sure that you're doing the right things. After this, I would say to check if your game does the same thing in a different game file. That's probably the next step after you're 100% certain you're doing all the steps correctly.