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:
twnicolaysen said: FI data updates does not appear to be the problem. Either Quicken is failing to grab the data from the FI, or, the FI is failing to pass the data to Quicken. In any event, the Quicken One Step Update transaction download process appears to be going through the proper steps and shows "complete" when finished, but the data do not appear in the register. When I check the account on line, it shows new transactions that should have downloaded to Quicken during One Step Update that day. Nor does it capture the Online/Statement Balance for reconciling purposes.