Can't Subscribe to FORUM -- Subscribing to THREADS Works Though

[NautiqueJeff]

1. vBulletin Version 5.2.3
2. PHP Version 5.6.24
3. MySQL Version 5.5.50-cll
4. Any Addons installed No
5. Does the issue occur in a default style? Yes
6. Does the issue occur using the English language provided? Yes
7. Error message on the screen "Sorry, you are not authorized to view this page (no permission)"
8. Browser and Browser version used. Firefox, Safari, Chrome
9. Did you clear the browser cache and did the error continue? Yes
10. A list of steps that can be used to recreate the issue. Sign in as a normal (non-admin) user, navigate to any forum, attempt to subscribe to that forum.

My users seem to be unable to subscribe to any specific FORUM. They are able to subscribe to individual threads with no issues, but when they try to subscribe to a FORUM, they get the error message above.

As an administrator, I am able to subscribe to forums with no issues.

Where can I change the permissions for the Registered Users group so that they can subscribe to FORUMS as well as threads?