LS220 - Disk on tw bays issue

[lordvault]

Hi guys,
I already have a ls220 nas, i bought the nass on the 2016 i think. Since there i has been using only 1 bay for my nas but recently my storage start to become full, so i decided to buy another disk.

Both disk have the same size, 2TB and are from the same vendor (seagete) the problem is that the nas never can format both disk correctly all the time i get some different issue, (disk1/disk2 cant be formatter). 

But if i put only 1 disk it works perfectly(any of them). I already use the "clean" on both disk as described on https://www.buffalotech.com/knowledge-base/cleaning-a-disk-in-windows-7-using-diskpart .

So idk what else do. How can i make my nas work with the 2 bay disk?.