@SKizale GP should install its extension automatically when a connection is opened. You can trigger the extension install after installing GP by running the following commands:

@sdagley, that did the trick. I ran those commands and tested the connection, but it still didn't work. So, without doing anything else, I rebooted and tried again, and it worked perfectly! I'll have to make up something that runs these post-install and reboots the machine. Thanks a bunch for your help. This had me stumped for a few days. 

Could you let me know how you set the portal to configure? Configuration profile with updated plist runs successfully but changes do not take affect.

@jennaferharris, did you reboot afterward? Mine did not work until I rebooted the machines.