Here's the error message in my Cloud Sync log, if that helps.
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https://services.quicken.com/institution-logins at 13:20:04 on 20211104 ***** -->
{"items":[{"code":403,"resource":{"id":"242296094881276161","status":"ERROR"},"errors":[{"title":"Illegal Operation: {0}","httpStatus":403,"detail":"Illegal Operation because Cannot change institution an existing connected institution-login","code":"QCS-0403-2"}]}]}