I have an Excel file I update on a daily basis. Today, after updating the file on one of my portable devices (HP Envy TS 17) I found OneDrive on my desktop PC showing an error that the 'changes couldn't be merged.' The presented solution was, "Open the files in Excel and save the copy that you want to keep.' This is the point at which the error occurred. It wouldn't open either file, the online copy or the local copy. The file opens fine from OneDrive on all other devices (including Android tablet and Android phone) and in Excel Online. I have opened the file on another device, saved it with a different name and now it opens on the desktop PC. I have encountered this error on two or three other occasions and the solution has been the same, open it on another device and save with a different name. I then delete the offending file and then rename the copied file.