Can’t open file on Word app on iPhone

1. Check the file format: Make sure the file format is .docx or .doc.
If the file format is not supported, try converting it to a supported format.
2. Check if the file is corrupted: Try to open the file on another device (computer or other cell phone).
If the file is corrupted, try to re-download or retrieve the file from the original source.
3. Update the Word app: Open the App Store and search for “Microsoft Word”.
If an update is available, click the Update button.
Make sure the Word application is updated to the latest version. 
4. Check storage space: Open “Settings” > “General” > “iPhone Storage” and check the available storage space.
If there is not enough storage space, delete unnecessary files or apps to free up space.
5. Re-sign in to your Microsoft account: Open the Word application and tap the Account icon.
Log out of your current account and log back in.
Make sure the account you are logged into has permission to access the file.
6. Check the source of the file: Make sure the file came from a trusted source.
If the file came from email or cloud storage, try downloading the file again. 
7. Open the file using another application: Try opening the file using another application (Pages or WPS Office).
If it opens, save the file as a .docx and reopen it in Word.
8. Contact Microsoft Support: If none of the above methods work, it is recommended that you contact the Microsoft Support team with a detailed error message and screenshots for further assistance.