Question Atx mobo's IO wont fit in ATX case

Apr 1, 2020
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Im building a new pc and for some reason the case I got is a cooler master masterbox k501L which supports ATX mobos and I got a z390 aorus pro wifi which is an ATX mobo for some reason I don't why the IO shield won't fit.
 
Im building a new pc and for some reason the case I got is a cooler master masterbox k501L which supports ATX mobos and I got a z390 aorus pro wifi which is an ATX mobo for some reason I don't why the IO shield won't fit.
The size of the I/O shield is universal. ITX or ATX, the size of the I/O shield is the same.
The I/O shield can be a tight fit.
Some pictures might help. Upload to imgur and link.