Credit cards missing months not importing

It's not clear what you mean by "missing months" but if you expect to get downloads from the time the account was opened until "today" you're almost certainly going to be disappointed unless you opened the accounts just a short time ago.

The financial institution, (FI), not Quicken, dictates how far "back in time" downloads are available.  A fairly typical period is 90 days, though some FIs do go back further than that.  Sometimes the FI's web site will have transactions earlier than what's available through a standard download.