This solution worked for me. I didn't have to clear the cookies and cache. I logged out of TT, logged off my Fidelity account and then signed into TT and signed into my wife's Fidelity account. TT was able to download the info for my wife. It didn't ask me for credentials. It must have figured it out since I had already logged into my Fidelity account. But TT wasn't smart enough to figure out that the interest and dividends belonged to my wife. I had to modify the 1099-INT and 1099-DIV manually for that.
