Issue Summary

The customer is using 'edit in office' instead of Companion.
However, when editing Excel files, MS Office Excel will always show warning of 'Keep my version' or 'keep server version'.
The customer can save by clicking 'Keep my version'.
However, the warning will show again when saving next time.

It does not happen for Word and Powerpoint.
The customer is using Windows.

This is reproducible on Data Center: (yes)

Steps to Reproduce

1. Open Edit in Office using the Office Connector
2. Create a test page, and put Excel file attached.
3. Go to attachments list of the page
4. Click Edit in Office
5. Click Enable editing in Excel (If there is not enable editing then the bug cannot be reproduced)
6. Save

Expected Results

The file can be saved normally.

Actual Results

The warning (Keep my version' or 'keep server version' ) is shown.

Workaround

Turn off "Enable Protected View for files originating from the internet" in Excel Trust Center settings.

https://www.automateexcel.com/how-to/protected-view-enable-editing/