When trying to connect to Global Protect on a Mac you may get an error message along the lines of network connection error. If this is the case it's likely caused from the lack of the proper certificate either not being there, or not being trusted. You can download the proper certificate here. Once it's downloaded you will need to open Keychain Access by pressing CMD + Spacebar and typing this.
Select login on the left side of this menu and open your downloads folder. Drag and drop the certficate into the field for Keychain Access. Navigate down to the certificate named paauth.atu.edu and double finger click (right click) and select Get Info.
Click the Trust drop down and select Always Trust for When using this certificate at the top. Close this window and try the VPN again. A full reboot may be required after making these changes.