For those using Mac OS X 10.11 "El Capitan” and having trouble with Pulse VON client this is how I was able to get it to work. 

Requirements:
1. Pulse Secure 5.1.1+
2. Symantec Cross Root Intermediate CA Certificate (https://knowledge.symantec.com/support/ssl-certificates-support/index?page=content&actp=CROSSLINK&id=INFO2550)

Procedure:
1. Copy and paste the Symantec Cross Root Intermediate CA Certificate text into a text editor.
2. Save the file with a .crt extension.
3. Double-click the file you created in the previous step
4. Select to add it to your “system” keychain
5. Double-click on the VeriSign Class 3 Public Primary Certification Authority - G5 certificate in the System keychain
6. Click the disclosure triangle next to Trust
7. Set the When using this certificate to “Always Trust”
8. Start Pulse Secure client and connect
9. Accept the certificate warning.