Dell PS5000 drive warning

Hello,

During firmware update of two PS5000 from ver.5.0x to 6.07 one of the devices raised a warning:

"One or more drives in the array are not approved". The other storage is fine. I followed the upgrade procedure. 

Any idea what this means and how can I identify the problematic drive. The storage was working fine before the firmware update.

Thank you,

Dimitar