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. The category seems to vary with the Loan Type you selected when creating the loan account in Quicken.
Thank you for taking the time to share the details of your experience and feedback with the Community, although I apologize that you have not yet received a response.
We'll need a bit more information to be able to assist.
Please take a moment to review the information available here and post back to let us know what version and release of Quicken you are using.
The more information you can provide will help the Community to better understand and assist.
Thank you,
-Quicken Tyka
If you haven't done so already, I'd say it's time to call Quicken Support on the phone and request help. Let them do a screen share session with you to review a download log file on your computer, to determine the nature of the problem and to figure out how to fix it.
Quicken Support: