message: Illegal Operation: {0} err code: QCS-0403-2

Try to Reset Sync so that the current cloud sync file is replaced with a fresh complete copy
Do note that a full Sync process may take many minutes to complete.

Log out of your mobile app, then do this on your desktop / laptop:

How to reset Sync to Cloud

1. Go to Edit / Preferences / Quicken ID, Sync & Alerts
2. Under the "Mobile and Web" group to the right, if present, click the "Reset your cloud data" link and follow the instructions until it is complete.

Also see https://www.quicken.com/support/troubleshooting-quicken-mobile-companion-app
and https://community.quicken.com/discussion/7856172/faq-common-mobile-web-sync-errors-and-solutions#latest