I've been dealing with this issue for over 6 months and I keep hoping Quicken will fix it without me having to post this message as I know other Quicken users have this issue. Apparently not.
I have 2 Quicken files. One is for my wife and I, and another for my mother-in-law. We have Schwab accounts and so does my mother-in-law; and I have the ability to view her accounts ever since my father-in-law passed away many years ago. I use my Schwab ID to download transactions into each of our Quicken files. That worked great until a year ago or so when that became a problem. There have been plenty messages posted and solutions applied, but the base problem comes back over and over again. The current solution is deactivate the account and clear the Schwab information. I do this for all Schwab accounts in the Quicken file. I then reconnect the files to Schwab. I will have about 2 or 3 successful downloads, and then the Schwab downloads in the other Quicken file will begin to fail. Rinse - repeat.
Please fix this problem!