The assets look really great, but are clearly not optimised for GB Studio.
The hotel, for example, uses over 200 unique tiles. (Which already exceeds the maximum number of unique tiles per scene, making it unusable in GB Studio.)
Try sticking to the 8x8 grid, and re-use as much tiles as you can.
Also, every tile can only have up to 4 unique colors, and there can only be 8 unique palettes per scene. Some of the tiles in the colored version of your assets use over 10 colours.