I ended up chatting with RedTeam again and found an agent who walked me through the steps to fix it. Thought I'd share it here in case anyone else has the same issue.

In RedTeam, when you are creating a vendor bill (invoice) and get to the approval screen you have to check mark the box that says "execute this disbursement upon authorization" and then approve it. This makes the Bill due date in QuickBooks Online be correct. This worked!