If a client accepts something from me, they pay for it. Period. Now, I have no idea what a client who represents a larger client is. I don't do middlemen, ever. If you can't make the decision, and can't pay me without approval, I won't write anything for you.
I've had publishers overrule editors about publishing a piece a couple of times, but I still got paid. I've also had businesses decide to take a different approach, but I still got paid. it's just not possible to earn a living as a freelance writer unless you get paid for what you contract to write, and I don't write anything except a query or proposal without a contract in hand. Writing an actual article, or other type of piece, before I know I'm going to be paid something, a kill fee at the very least, is a complete waste of my time.