Empty cells are ignored by XLApp so to make a cell visible it should have a value or you should Name it and change the Type (right-click → Format Cells in Excel) from general to Text.

Similarly Lists should also have an item selected. If there is empty data in the list then it will not appear in XLApp.

In case you are facing unusual behavior, test the app on desktop chrome browser. Use Developer Settings (ctrl+shift+I) and see if there are any errors that appear in the console window.

Sometimes the browser might also cache old files so Refreshing the Page with CTRL+F5 should fix caching Issues.