Why am I unable to place any tiles on my map?

Questions
1

The title says it all. I have so far been unable to place a single tile from my tileset on the map. I have a feeling the issue is stemming from the fact that I’m using single pixel tiles. Can I get any direction on this front?

Here’s an image of what I’ve got so far: Imgur: The magic of the Internet

2

The problem isn’t the 1px size of the tiles, but the fact that you have Terrain Fill mode on, but no valid terrain set selected. Disable this:
image
and you should have no trouble using your 1px tiles.

3

Thankyou that worked