Make Private not available on SanDisk SD Card files on phone

I have a Samsung Galaxy S5 with a Sandisk 32GB SD Ultra installed and a SanDIsk 32GB Dual USB Drive (external). I’ve installed the SanDisk Memory Zone app and it allows password protection for internal phone memory and for 32GB Dual USB Drive (external) but NOT the Sandisk 32GB SD Ultra card installed in phone.  Live Chat at SanDisk said to post in forum as they do not support SanDisk Memory Zone.