custom thumbnail is not working??? it would be REAALLY cool and helpful if i could add my thumbnail to my newest ych, but alas, FA thumbnail broken >:(

sighs. I updated it many times in submission editing, but i read that FA stores custom thumbnails as cache so it might take a while..? if thats anything like avatar displaying though, it could be days X(
and i just dont understand why it didnt work because i submitted it WITH the custom thumbnail.. UUGH