Fix oneDrive error message: Your file wasn't saved because we cannot merge your changes with ch

Workaround fix for this error message: Your file wasn't saved because we cannot merge your changes with changes made by someone else using an older version of excel

1) Right-click oneDrive
2) Click settings
3) Click the Office tab
4) Uncheck "Use office applications to sync office files that I open" or choose the "always keep both copies" option.