It sounds like your Excel file may be corrupted, which can happen for a variety of reasons such as a sudden power outage or a virus. Fortunately, there are a few things you can try to repair the file.

1. Open Excel in Safe Mode: Try opening Excel in Safe Mode by holding down the Ctrl key while opening Excel. This will disable any add-ins that may be causing issues with your file.
   
2. Use the Open and Repair featu Open Excel and click on File Open. Browse to the location of your file and click on the drop-down arrow next to the Open button. Select Open and Repair and see if Excel can repair the file.
   
3. Use a third-party tool: If the above methods do not work, you can try using a third-party tool such as Stellar Repair for Excel or Kernel for Excel Repair. These tools can repair corrupted Excel files and recover data from them.
   
4. Recover data from a previous version: If you have a previous version of the file that was saved before it became corrupted, you can try recovering data from that version. To do this, right-click on the file and select Properties. Click on the Previous Versions tab and select the version you want to restore.

It's important to note that repairing a corrupted file may not always be successful and you may lose some data. It's always a good idea to regularly backup your important files to prevent data loss.