If yes:
Check the box "Show Hidden Files", and then continue normally.
If no:
Close out File Manager, and go back to cPanel homepage.
Scroll down, and on the bottom where the cPanel copyright is,
click "reset all interface settings". Looks like nothing happened, right?
Now scroll back up, and click File Manager. The popup box will
now show! Check the box "Show Hidden Files", and then continue normally.
That's all!