TileSet image dimensions

Hi! I am very new to game development and I have just started playing around with Tiled and I love it!

However I am getting this error in my web browser:

Tileset image dimensions do not match expected dimensions. Tileset width/height must be evenly divisible by Tilemap tile width/height.

The grid im using for my map is 30 tiles x 15 tiles with tile sizes 32px x 32px. Some of the tiles in my tilesets (from collection of images) are 64px x 64px. Is this not allowed or am I missing something?