I think your problem was the leaf hops, but here's how I do it with pellet hops in a bag.
Open both the input and outlet valve, You should see some bubbles. If you're like me and your hoses are longer than they need to be, pick up the slack to remove even more bubbles. Turn on the pump. It may work at this point or you may just see more bubbles. If so, stop the pump and repeat the above, until it starts to flow. It will. Don't run your pump dry for any length of time.
One other thing I do sometimes is I connect my inlet pump hose (male OD's on both ends) to my faucet via a short piece of silicone tubing, turn on the water and then the pump. Once I'm sure the pump is full, while holding the hose ends up, I connect them to the BK. I get a shot of water into my wort, but it's not that much.
I really think you need to bag your hops or clogging will continue to haunt you. The pump can handle some pellet hops that escape from the nag or even those that you dump in for aroma at the end of the boil. It just can't handle a massive amount of them.