When you open Microsoft Excel, you get this message:
Microsoft Excel isn’t currently your default program for viewing and editing spreadsheets. Do you want to select file types that Excel should open?
When you click Yes, it tells you that To change your default apps, go to Settings -> System -> Default Apps. When you go to the Default Apps program, it’s a nightmare changing the defaults to open spreadsheets with Excel.
Installing Windows Updates or upgrading Office can cause Excel to become unregistered as the default program for viewing and editing spreadsheets.
To fix this, navigate to:
Control Panel\All Control Panel Items\Default Programs\Set Default Programs
Then click on Excel in the left hand side and click “Set this program as default”. This should make Excel the default program for all the file types it supports (the default program for viewing and editing spreadsheets).
If Excel isnt’ in the list of default programs, Excel has become unregistered from the list. Reinstall or repair Office (Excel) to fix this. If you can’t be bothered doing that, just right click some Excel file types in Windows Explorer and click “Open with”, then tick the box to always open with this program, then select Excel. This probably won’t make the “Microsoft Excel isn’t currently your default program for viewing and editing spreadsheets” message go away, but it will fix the symptoms. You can then start Excel and tick the box to not show this message again, to get the message to go away.