It actually is charging. You may see a the battery icon "Not Charging" but because of the power requirement for an iPad, it doesn't recognize the power going from the hub. Charge it for 1 hour you will see your big green battery icon getting filled and percentage higher than before.
Note: The Hub's USB 3.0 ports outputs 900 Mah (0.9amps). Because of the sheer compact size of the hub, the USB 3.0 ports will not output at times a full 0.9AMP. Some devices such as an iPad will charge noticeably slower, since it has a big battery. Since it is not directly connected to a power source such as a wall outlet, it will charger slower.
Note 2: Fast charging on IPADs happen from 20% to 80%, thus from 80% to 100% will be charged regular. Our hub does not have a fast charge since fast charge requires a 29W power adapter which is much higher than the 12W power adapter that came with your iPAD.