WD My Book Studio 2 failed to recognise both drives after dismounting and erasing on mac


My 4TB WD Studio 2 broke down, and after checking with Disk Utility on mac it told me to backup if possible and change drive. I decided to dismantle both drive and test them on an external HDD docking system. both were unreadable with Disk Utility but I could erase them. That is what I did for both disks. Then I put them back into the Studio 2 and put power on, light was not blinking, it was still so I plugged into the mac but mac did not recognise the drive and asked me if I wanted to erase, I did and now I got one drive at 4TB instead of 2…
What did I do wrong ?

thank you in advance for your answers

Hi Petri_de_Pita,

It seems that issue is with the My Book Studio enclosure. You should try to check both drives in another My Book Studio enclosure.