Can’t set up payment plan

Keep getting the below message when trying to set up a payment plan and need help. I’m in the process of buying a home and I’m being asked to provide a copy of the installment agreement but I’ve been trying for days and it simply can’t get it. I’ve tried selecting every payment plan possible, 12 months to 36 months and tried custom amounts and get the same error no matter what.

“Payment plan submission error

We are unable to process your request for a long-term payment plan. Please try again later.”

Any advice?