I've got some insights about your issue in logging in to QuickBooks, @menobits-outlook.
Based on your scenario, you should be able to log in using the new credentials since the update was successful. You'll have to ensure that you enter the correct login credentials for your QuickBooks Online company. To check, you can click on the Profile icon then select Manage your Intuit Account.
After that, go to the Sign-in & Security section. From there, verify if all log-in information is correct and if it matches what you enter when signing in.
If so, refresh the page and try to log back in. In case you'll get the same problem, I suggest performing some basic troubleshooting steps to resolve the possible browser-related issues.
To start, access your QBO account using an incognito browser. Here are the shortcut keys to open it: