Stock cash basis amounts were changed to zero
MUCH more info needed, starting with, if you're still running QW2017, as your profile reads, the conversion shouldn't have impacted you as all as the ability to download into 2017 ended YEARS ago.
Next, what Q product, what release of that product, what type of accounts at Fidelity.
And, I don't recall any posts about such a change … so the conversion might be merely a coincidence.
Running Quicken Premier R64.30 Build 27.1.64.30 - Traditional IRA account —-Fidelity is changing it's transaction download method with Quicken. Quicken has developed a procedure to follow to setup the download connection. When I run the procedure Quicken sets up a new account and the stocks listed in the new account show zero cost basis. The old account shows the cost basis for all the stocks in the account.