Hi Edward1230,
Based on the description, please follow the following steps to troubleshooting:
- Please first restart your Mac and open the Excel to see the outcome.
- Run your Mac in Safe Mode to see whether the issue goes away.
Disclaimer: *Microsoft provides no assurances and/or warranties, implied or otherwise, and is not responsible for the information you receive from the third-party linked sites or any support related to technology.*
If this issue still exists, please perform the steps bellow to help narrow the issue.
- Does the same issue happen when the file saved on Windows?
- If the issue happens with the specific file or all csv file?
- Please show us a screenshot of the normal csv file and the Data missed csv file.
4. Try copy the same content in mac excel and save again, see if it’s character problem.
- Try copy the same content in online excel and download it, see if it’s character problem.
In addition, I’d like to collect the Mac version for the further assistance.
Regards,
Jerry