I tried with my n810, and I don't have any problems using ls -a to view hidden files. I completely agree with sjgadsby, try creating a hidden file in known location and try using ls -a.

I used your example and installed openvpn - when I navigate to /etc/openvpn - there were are no files listed in that directory.

Start with sjgadsby's post first, and if that fails - the question would be have you tweaked / modified anything on your system that would fundamentally break viewing hidden files (not sure how).