Hi there, @Ashikul. Welcome to the Community.
The error message you're experiencing in QuickBooks Online is a standard safety feature designed to prevent conflicts when multiple users try to access or modify the same record or settings at the same time. To resolve this issue, you'll need to wait until the other user has finished before continuing your tasks.
Since you're the only user, the system might still be recognizing a previous session from your own activity. For instance, it may think that the account is still open or in use, even though you're the only one logged in. In this case, please wait a few minutes before trying again.
If the issue persists, try signing out and signing back in. This can refresh your session and often resolves temporary problems. Additionally, you can clear your browser’s cache to remove any stored webpage data that might be causing the issue.
You can also use the Audit log to check if any other user has accessed your account features.
Please keep me updated or reach out if you need any further assistance. I’m here to help.
