Excel download not working in mac and not show in firefox?

Reka

Hi
I am newly entry to datatable working . I am try to download a csv,excel,pdf format. Successfully downloaded a csv,pdf format. But i am facing problem excel format.

1)If i click a excel sheet ,downloaded the excelsheet(.xlsx) format.But i try to open a file,data is empty. i cannot see the data.
This problem facing only for mac.

2) excel button not showing in firefox.

please give solution for above two problem