Just now I had to reauthorize with Schwab, and Quicken failed to link my existing accounts. Note that I did not uncheck any accounts on the FI's website:
Then I hit Finish and went into one account and did Set up download. Quicken only defaulted to link one of the accounts, and I specified to link the other:
This happened the same way in another Quicken data file I track these accounts in. Also it happened previously when reauthorizing with Fidelity. Problem reported. See for previous report: