Hi there,
I think it’s just not going to fit? or the pins are off or inverted or ? total guess here I don’t have a samd21 they have always been too light weight for my prototypes any way ,You may look at this link ,
SAMD21 (arduino mkr zero) with TFT 3.5 ili9486 albeit not directly about round eye display, but
worthy of a look imho, what frequency is your spi or clock?
GL 
PJ