Lastly, as an administrator, I am able to see details about your Cloud instance.xlsx format, please let me know which one you are using.
Can you see if you have an update availble to your Excel since you seem to be behind a bit now from the most recent available? If you have an update, please apply it and let me know if your edits are changed.I uploaded it to my Cloud Confluence instance, embedded it into a page, and then used the Atlassian Companion app to edit it.
I am now running Excel 15.36 on macOS Sierra. So I downloaded Office 2016 since my copy of Excel was from Office 2011.
