Android 4.1 tablet Model M736 not recognizing keyboard when connected through 4 port usb hub
Connect a self powered USB hub and try again.

USB-OTG ports often provide little power that's suitable for one device only, but may already fail for power hungry devices like very fast USB thumb drives, wifi dongles or 2.5in USB hard disk enclosures. Your setup very probably draws too much.

You can use any 3rd party USB power bank if you need it on-the-go. Your hub may have a power input connector already. Finding the right cable might be an issue though. Here's some related info, someone asked this for the SGS i9000 which doesn't provide power at all: USB host mode not working on Samsung Galaxy S using CyanogenMod