The issue is really that you don't have the borrowing record, and a motorhome (or any other vehicle) is really poor security. Your situation sounds much like mine. Assets to earnings, assets to debts high, no real consumer borrowing in the past 10-15 years, lenders don't have much to go on. Hate to liquidate pre-tax assets because I'll have to pay taxes on them.
You can almost always get a loan, it becomes a matter of how much interest you are willing to pay, and what you can put up, other than what you are buying, for security.
Solution is to borrow against those good assets (real property, insurance cash value, retirement savings). Mortgage on your home would be lower interest than vehicle loan because the security is better. Loan against insurance or retirement savings may be lower interest, and you will be paying interest to yourself.
Or else you can continue shopping on a poorly secured loan, sooner or later you'll find a lender who will come up with an interest rate high enough to cover the risk. Interest vs risk scale is almost limitless, I've had to try to rescue borrowers caught at more tha 100% per year with their collections of small short term unsecured loans.