Why does Excel for iPhone say "Can't upload—We can't merge your changes with those made by someone else"?

Question

I've used Microsoft 365 for Mac and iOS for years. I use Excel for a spreadsheet to record twice-daily glucose and blood pressure readings to share with my doctor. I use it mostly on my iPhone, but also on my Mac; the file resides in my OneDrive account. Yes, I have OneDrive installed on my iPhone and on my MacBook Pro. For what it's worth, I also use Microsoft 365 and OneDrive for Windows 11, which runs in a partition on my Mac as a VM. On occasion, I access this file in Excel for Windows on my Mac.

Mostly, the spreadsheet behaves itself, but from time to time Excel tells me, "We can't merge your changes with those made by someone else." Excel give me two choices: I can save a copy of the spreadsheet, or I can discard my changes. Over recent years—and twice this week—I've saved a copy of the spreadsheet and proceeded with keeping my records on the copy. I've lost track of the number of copies I've made of this very same file.

I really don't understand what's behind this error because NOBODY ELSE USES THIS SPREADSHEET! Over and over, I've asked myself, "Who's this 'someone else' who's tinkering with my spreadsheet?"

I know there's an explanation for this very annoying behavior, but my skills don't go far enough to detect the cause. I hope someone here can lead me to understand the problem and perhaps even keep it from happening again.

Answer 1

Hello,

This issue can occur when the same file is edited on multiple devices through OneDrive. It’s not necessarily someone else editing it, just a different device you’ve used.

For instance, imagine you open the file on your Mac, make some changes, but due to an unstable internet connection, those changes don’t sync to OneDrive before you close the file. The edits remain only on the local Mac copy.

Later, you open the same file on your iPhone. Since the Mac’s changes never synced, the version you see on your iPhone doesn’t include those edits. If you then make additional changes on the iPhone, OneDrive will eventually detect two conflicting versions once your Mac reconnects and syncs—leading to a version conflict.

To avoid this, always save your file after making changes and check the OneDrive cloud icon to confirm it has finished syncing before shutting down your device. This helps ensure all edits are properly saved and synced across devices.