[Zubersoft]

Then that's not related in any way to the update, as version 3.8.25 isn't available yet through the Microsoft Store. The next thing to check is to go to C:\Users\<your username>\AppData\Local\Packages\41730Zubersoft.MobileSheets_ys1c8ct2g6ypr\LocalState and see if you have a Microsoft.AppCenter.Storage file. If so, delete that, and try restarting the app. If this doesn't help, try renaming default.xml to default_backup.xml and restart the app. Lastly, try moving the entire LocalState folder somewhere else on your machine and restart the app. If it doesn't come up, uninstall MobileSheets and reinstall it through the Microsoft Store, as it would appear the application installation is corrupted. After reinstalling, verify it comes up, and then move the LocalState folder back (and rename default_backup.xml to just default.xml). 

I should mention, if you are not logging into Windows with the same email address you used with the Microsoft Store to purchase MobileSheets, you really should do that to avoid issues.

Mike