Where do I find most recent Quicken for Windows update?

The announcements of the updates to the releases are supposed to be maintained in: Product Releases and Announcements: Windows

The latest release update is supposed to be available from within Quicken: select Help > Check for Updates

If you have issues applying an update from within Quicken, the latest Mondo patch is supposed to be available at: https://www.quicken.com/support/update-and-patch-20182019-release-quicken-windows-subscription-product

If you are having difficulties applying an update, I suggest you perform a clean uninstall, install and update.  If you haven’t already, you may want to review: https://www.quicken.com/support/using-qcleanui-uninstall-quicken 

Schwab remains unstable since they terminated their Direct Connect server.  I suggest maintaining the accounts manually until the dust settles.

If the issue with First Financial Bank NA checking account persists after you have updated Quicken to a recent release, please provide the full name of the financial institution and the connection method being used: open the register, press Ctrl + Shift + E and select the Online Services tab.