Hi Tommi,
Please firstly try the following steps:
- Open Excel>File>Account>sign out the existing account>quit Excel.
- Open Control Panel>navigate to Credential Manager>remove all Microsoft related credentials in Windows Credentials and Web Credentials.
- Restart your computer. Open Excel and then sign in with the account which is related to that Excel file.
- Open the file to check the outcome.
If the issue persists, please let us know the following things:
- Do you run into the error each time you want to open that file? Or just when you find other users are editing or just edit that file?
- Open Excel>File>Account>capture a screenshot of all info under Product Information. Please mask your account info in the screenshot.
Best regards,
Tim