MyBook Duo 16TB Disk does not mount anymore

Suddenly with no reason MyBook Duo 16TB does not mount anymore. Disk Status from WD Utilities seems fine, but does not auto mount anymore, if I try manually get this error:

Could not mount “disk3s2”. ( error -119930868.

Attached status:

Any ideas? I have lot of critical files on this device…
Disk is still under warranty, what should I do?