Let's first access your Intuit account using a private browser or an incognito browser. This way, we can isolate this concern for possible browser issues. You can use either of these keyboard shortcuts:
Press the Ctrl + Shift + N (Google Chrome) keys on your keyboard.
Press the Ctrl + Shift + P (Firefox or Microsft Edge) keys on your keyboard.
Press Control + Option + P (Safari) keys on your keyboard.
Select the User ID, Email Address, or Password section.
Make your changes.
Click Save.
Once you're able to successfully access your account, you can try clearing your browser's cache to delete those temporarily Internet stored files. Also, let's make sure you have the correct login credentials by clicking the I forgot my user ID or Password link in the Sign In page. You can refer to this article for more detailed steps: Reset your password or recover your user ID for QuickBooks Online.