I have been asked to reauthorize my accounts at both Fidelity and Chase in the past couple days. For both institutions, I have reauthorized all my accounts on the institution web site. In the acknowledgement, Quicken lists all the account numbers as reauthorized but for some reason does not connect some of those numbers to the actual Quicken account and so disables download for those accounts.
I then do an "Add Account" for that institution and again authorize all the accounts. This time, Quicken correctly links the online account to the existing Quicken account. For the Fidelity accounts, I then had to manually reset the money market accounts to be treated as cash.