I'm a dummy. I failed to see this little slim line has 2 USB connectors on the back. One for data and the other is a power connector. With both connected now, it works perfectly!
Drama solved.
:whack:
Nice!
Electrically, you probably shouldn't be using this kind of setup. If the drive does not have a socket for a power adapter, you should consider using a self-powered hub. These hubs usually don't have overcurrent protection (against the specs), while the Deneb has a 0.5A protection for each port. However, Michael Böhmer does not recommend routing the power of the different ports to the same device.