This will sound harsh but:

> The software we make isn't software for software developers

Like most software companies on the planet.

> we need to improve developer understanding of how our customers use the product

I'm pretty sure no dev said that, ever. It's the job of the CEO, managers, project managers, sales people, etc. Anyone but the devs who would do anything not to get fired nowadays.

> encouraging devs to reach out to customers

It's NOT their job. I would be very reluctant to contact customers directly. Most clients don't know what they want, and devs want to please anyone as long as it involves coding. You need direction. Also, when customers have impossible demands, managers will lie that it's possible and try to sell something different. No dev will tell you that something impossible is possible. We are not salesmen.

> We've also pointed to existing bug trackers

That doesn't mean anything at all. Which bug tracker?

You seem very confused about what a dev is supposed to do. You need a PO (project owner) or PM (project manager) or anyone that can understand the customer's needs. Right now you have none and you think your devs should find the issues themselves, or magically find what the customers want.

Feel free to ask if you have more questions.

Edit: the last time I spoke to a customer, I gave a few technical details and no one cared. I don't know what is his IT department, what is his budget, who I have to contact, I know nothing. That's the job of a whole team (CFO, sales, etc). It feels like one of those niche projects where anyone can do anything and the client is supposed to accept that with some kind of unlimited budget, am I wrong? (Edit: "Payroll, HR, and Workforce Management" no wonder your devs are not understanding what you do, you need serious training, simulations, or anything to entice them, but speaking to customer would be a bad idea).