Why does Unity turn my texture into a square when importing?

Hi

I am trying to import a png picture into my project as a texture. However whenever I import it, instead of keeping its normal length and width as set in my image editing program, it turns into a square. I've imported textures before with the same sort of settings and they have retained their normal length and width. Its just this texture that doesnt work. I've tried renaming it in case there was a letter/symbol that was causing the problem and i've also tried changing the width/length in my photo editing program but it still doesnt work.

Thank you in advance