If you share an Excel file that is stored in your OneDrive for Business, it is possible for those you have shared the file with to edit it collaboratively (at the same time) as long as all users open it up through Excel Online (Excel through Office 365 on the web at https://portal.office.com). However, if one of the users opens the file in Microsoft Excel, the file will become locked until the file is closed, preventing anyone else from editing the file. Once the file is closed, it may remain locked for up to ten minutes. The error message that appears in Excel Online does not indicate what user has the file locked:
To find out who has a file locked, perform the following steps:
1. Open the file for viewing in Excel Online by clicking on the file in your OneDrive for Business through https://portal.office.com
2. Once the file is open for viewing in your browser, click on "Edit in Excel" and choose "Open in Excel" to open it in the Excel program that is installed on your computer.
3. Microsoft Excel will open the workbook in read only mode. In the header at the top, click on "Edit workbook"
4. Excel will advise you who has the file locked, and you may contact them to ask them to close the file, or you can save a new copy of the file for editing.
