Theres currently a bug with tk2dCamera and the camera preview
It uses a custom projection matrix, and the camera preview (and the camera bounds in the viewport) doesn't actually reflect what is seen by the camera. The only way to correctly display the output is to look at the game window.
In your case, my guess is the your tilemap is very very small compared to the the output - what is the spritecollection setting orthoSize & targetHeight? It should appear correctly (at the right scale) if the tk2dCamera setting is ticked.
My best advice to figure out whats going on is to tick the Use tk2dCamera tickbox on the spritecolleciton, and then place one sprite in the scene at 0, 0, 0 and note where it appears in the game window. It should be at the bottom left of the screen. Keep in mind that if you do this and revert, you will have to set up your orthoSize & targetHeight parameters on the sprite collection again.
It does make sense when you understand whats going on, unfortunately with those two bugs there, it makes it really hard - I apologise for the inconvenience, and I am actively working out a nice solution to this.