Content creation is fantastic! But it can sometimes get bogged down in the details and the process.
First, figure out how your client ticks. They have other things to worry about, so find the best way to tap into what works for them! For example, we created a tool with a simple approval process that's easy to use.
Also, make sure you have more than one contact for your clients. Does the approval person have a receptionist? Assistant? THey may be able to help.
Finally, as Search Engine Journal said, "If nothing is working, just ask! You’d be surprised what you can learn from asking plainly why they’re not approving content."