My Cloud EX2 Ultra 5TB GPT USB drive not recognized

Hey, I’m new here so if I make any mistakes with this post please correct me.

I own a 16TB (2*8TB) WD My Cloud EX2 Ultra. I want to use two external USB 3.0 hard drives. I have used a 2TB Intenso hard drive now for many months and it worked great. The second is a 5TB WD Green HDD in a no name enclosure. This one of course uses the GPT partition table. I tried NTFS, exFAT, ext4 and ext2 but it never gets recognized. Is there any way for me to use this HDD with my My Cloud?

Best regards and thanks in advance
Colin

Soo with some help from the WD support hotline I found a solution. The problem was NOT the GPT layout. The external drive I used had a hidden Virtual CD Drive. This announced itself with the LUN ending on “0”. The drive itself got a LUN ending on “1” which according to this Externes USB-Laufwerk wird nicht bereitgestellt, nicht gesehen oder von einer My Cloud erkannt is not supported. In my specific case this http://aps2.toshiba-tro.de/kb0/SPD4603LR0000R01DE.htm worked.