"Persistent connection is disabled" - can't enable

8.5 RU3 running on WS 2012 R2 NS.

Settings --> Notification Server --> Notification Server Settings

Persistent Connection: On

Settings --> Agents/Plug-ins --> Symantec Management Agent --> Symantec Management Agent Communication Profiles --> dept-deploy.dept.example.edu

"Persistent connection is disabled".

I click Edit and enable it.

I click "Save changes" at the bottom of this page.

...and every single time, it flips itself back to "Disabled".

Am I missing something?

Thanks!