One has to either select Open In from the OS5 My Cloud app interface, then select the appropriate app to open the file. Or download the file to their mobile device then try to open the the file in an Excel app on their mobile device. More information on how to manage files in the OS5 My Cloud mobile app can be found at the following WD Knowledge Base article.
If one uses the forum search feature (magnifying glass icon top right) to search the OS5 subforum they’ll find at least one past discussion on this issue.
