Error message: File couldn't open in protected view

Hi rkarthik19,

Thanks for posting in our forum.

Based on your description, there have some specific Excel files that would get the error message as the following screenshot. May I know if the issue files are related with Outlook? Anyway, have a try with following suggestions to fix the issue.

1.Run the Office Repair Tool.

1. Press Win+R and type Conrtol Panel in the window
2. Click uninstall a program under Programs tab
3. Select the Office version you have installed and click Change button on the top bar
4. Leave the Quick Repair option selected and click Repair

Check the result after the repair process is completed by opening the issue file in Excel to see if everything back to normal. If the issue persists, try the Online Repair option again.

2.Disable Protected View

1. Open Excel and click the Options in the bottom-left corner.
2. Click on Trust Center and click Trust Center Settings
3. Switch to the Protected View tab and uncheck all options.

Then click OK to save the changes, and check if the issue disappear when opening the files again. But this is only a workaround currently and make sure all files are safe and have a strong antivirus installed on the local PC.

3.Rename the file and change the file type.

May I know if these issue files have been downloaded on the local PC? If so, please check if their file type is .xlsx as the newer Excel format if you are using the latest version of Excel. After opening the file with the workaround you discovered, click File and click Save a Copy. Select the location as you want(local PC is recommended but OneDrive is also good) and rename the file and select another file type.

If the issue persists after trying above suggestions, please share us the current version of Excel on your side so that we could offer some other appreciate support based on your scenario. Open Excel > click File > click Account and share the screenshot here.

Appreciate your effort and patience on this issue, we will try our best to offer any help to fix the issue.

Best Regards,

Mia