Every time we open a standard Excel 2016 XLS worksheet or CSV that is stored on DropBox, Excel seems to open the file and then crashes. When we try to open the XLS again, the XLS opens perfectly and has the Excel recovery window showing the original file that failed.This does not happen for XLS files that are stored on the SSD of the laptop so must be something to do with storing the file on DropBox? We are using selctive sync in our DropBox environment and this problem has only started happening in the last week or so.
Can you just try quitting the desktop app and try open one of the Excel files from within the Dropbox folder again to see if you get the same behaviour? If you're not familiar with quiting the app then you can follow the steps below: