Hi Le,
Appreciate your kind patience.
The next suggestion is to right-click on a .xlsx file>click Open with>check if there shows the Excel app as an option. If not, click More Apps and locate where the Excel app is installed.
- If you are using 32-bit Office, go to C:\Program Files (x86)\Microsoft Office\root\Office16.
- If you are using 64-bit Office, go to C:\Program Files\Microsoft Office\root\Office16
For reference: Excel not default for .xls files - Microsoft Community
Some customers resolved the same issue by this way and kindly post back if it failed to work on your side. We will continue to help.
Best Regards,
Mia