For whatever it's worth ... I would not bother attempting to activate any loan or mortgage account for downloading. (Not discussing LOC or HELOC accounts here)
An online-connected loan or mortgage account does NOT have a transaction register. All data shown in the account come from whatever information the bank downloads to you ... if this process works at all.
As a result of being connected, the scheduled payment transaction reminder cannot transfer the amount of principal paid into the (non existent) account register and must use a category, usually something like Loan:Principal, instead.