Hi @Coates, Jocelyn ,
Have you tried to check out this file in SharePoint? Dose the issue happen to all user?
I am not able to reproduce this error. You could check out the excel first then open it, if still get this error message you could make sure this file is not checked out in library settings > Manage files which have no checked in version.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.