Turn off the demographics coloring: City -> Layers -> All BLDNGs with shading

If that doesn't work, try hiding all the layers that start with BLDNG

Still about a week left of the competition, which means it is still enough time to pick and map a building (plenty of small ones available if you want to do something quick).

I'll also point out one thing to everyone planning to submit their map to the atlas too (hopefully most of you). The atlas has it's own navigation bar off the side of the map, so I do not need that little navigation box CC3+ makes for multi-floor maps in the lower right corner. Because I usually need to rename the map files when putting them into the atlas, the links in that box will be broken anyway, so I'll just have to delete it. So I would be pleased if you just remove the entire box (including the hidden hyperlinks (view -> Show Hyperlinks to show them)) before you hand in the map or at least keep in mind how the map will look when I remove it. Thanks.

You need to move the floors back to the BACKGROUND (FLOOR 1) layer too. The corridor tool operates on both floors and walls, and expects both to be correct for it to recognize an existing entity in your map as a dungeon room/corridor to work with.

Check this FAQ topic:

For symbols, you can just hit the options button on the top of the symbol catalog option and turn off the option that symbols choose their own sheet.

That said, I recommend you don't do this. This feature is a huge time saver when mapping, and really helpful to ensure things go to the right sheet. It may sound like having more manual control is a good idea, but in practice you're just setting yourself up for much more work, and a lot of symbols on the wrong sheet because you forget to change it.

I recommend learning to use the feature in your workflow instead of turning it off. See this FAQ entry for some information: