Just my 2cents' worth … I would not bother attempting to activate any loan or mortgage accounts for downloading. I would just simply set them up as "offline" (manual) loan accounts with a Scheduled Reminder to record the monthly payment from your checking account. (Not discussing LOC or HELOC accounts here. They should be set up like credit card accounts)
At least in Quicken for Windows, 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.
Effective with Quicken Windows 2018+ you can deactivate an online-connected loan account and regain full control over your transaction register. However, you should still review the Scheduled Reminder (or Memorized Payee List entry) associated with the monthly loan payments to ensure they now transfer Principal to the loan account register and not to a Category.
If you're a Q Mac user, you should be able to do something similar about setting up and maintaining an offline mortgage account together with a correctly calculated Scheduled Transaction Reminder for the monthly payments from your checking account.
UKR said: It is the bank, credit card or mortgage company which ultimately decides whether they allow "third party data aggregators" like Quicken, Intuit, etc. to access their computer systems on your behalf. Recently, "for security reasons", more and more banks decide to block these service providers, rendering a good feature useless. To avoid these problems maintain your mortgage account as an offline account, as described earlier. This way you'll have a properly working mortgage account register with a correct balance and your payments will be made on time.