While attaching Excel to window, the selector validation fails after capture of the excel window. Initially it shows as green(validated) but after reclicking on validation button for the selector, the validation tab turns red(Invalidated):
Below images provide the validated and invalidated selector screens:
If the above suggestion (to indicate element on screen) fails, you could also attempt to repair in UiExplorer. In the second screenshot you submitted where the validation fails, see that in the top menu bar, ‘Repair’ becomes highlighted.
Going through the steps of repair, UiPath will attempt to automatically detect and fix whatever validation errors are occurring. Hope this helps!