From there, go ahead and attempt import the same QFX file as you normally would to manually download. You should receive a prompt to add the account. Once that is done, see if you experience the same issue in this test file. From there, you can then switch back to your original file.
Follow the steps below to switch files:
Quicken will list the most recently opened data files, with a checkmark next to the file you are currently viewing.
Let us know how it goes!