The HR department typically does not have a budget.
As much as the head of human resources may like your product, they probably can’t buy it.
The same is true for other back-office cost centres (e.g. finance or legal). They don’t have money.
If you’re looking for a sale, focus on the departments with big budgets.
As a rule of thumb, these are the ones found close to the revenue.
They include the CEO’s office, sales, marketing and product.