Bug Sprite can not be put into any Sprite Fields

I have 2 Sprites with the exact same settings. The only thing varying is the size, one is 8x8 and the other 32x32. The 8x8 one can't be dragged into any Sprite fields nor can it be found by the sprite search when one clicks on the field. (When i try to drag it into the field it shows this red circle icon with a line)
Does anyone have any idea on how to fix it?

 

theres a difference between sprite and texture, maybe your texture hasnt generated a sprite asset or you are dragging the wrong thing

 

I found a fix. I have to go into the sprite editor for each of them and manually slice them (to the same size of the image)

 

If your image contains only single sprite, change the "Sprite mode" from "Multiple" to "Single". That way you won't have to manually slice them in sprite editor. "Multiple" mode is for cases where single image contains multiple sprites, and such situations manual slicing is required.