What is preventing the menu from displaying the ticket application link

I would expect this to work. Just out of curiosity, have you tried clearing the data cache and recycling plugins?

I have been digging in the code, and I cannot see where the type attribute is used to instantiate an object that inherits from CustomNavigationItem.  So, the platform never instantiates our custom navigation item that inherits from CustomNavigationItem.  It is listed in the default xml but never comes out of $core_v2_customNavigation.Deserialize method.

<navigation id="d97da859e0f54f7da0a0d1672947ffff"><links><link type="Telligent.Evolution.Controls.SingleGroupCustomNavigationPlugin, Telligent.Evolution.Platform" id="ad164b2a-370c-415b-bc34-a89e1380c6a3" configuration="group=Group%3D-1&loadedFor=1002" label="Home" /><link type="Telligent.Evolution.Blogs.Plugins.CustomNavigation.GroupBlogsCustomNavigationPlugin, Telligent.Evolution.Blogs" id="113e18ef-8b6b-41f4-baf1-46ee9a38e829" configuration="group=Group%3D-1" label="Blogs" /><link type="Telligent.Evolution.Api.Plugins.GroupLeaderboardsCustomNavigationPlugin, Telligent.Evolution.Platform" id="c393f33b-3a31-4f25-8822-4084a41299d2" configuration="group=Group%3D-1" label="Leaderboards" /><link type="Telligent.Evolution.Forums.Plugins.CustomNavigation.GroupForumsCustomNavigationPlugin, Telligent.Evolution.Forums" id="bfc84935-bef1-4464-95b9-65b82930e643" configuration="group=Group%3D-1" label="Forums" /><link type="Telligent.Evolution.MediaGalleries.Plugins.CustomNavigation.GroupMediaGalleriesCustomNavigationPlugin, Telligent.Evolution.MediaGalleries" id="e02e429f-dfd0-4895-9b66-dc13c1da8b73" configuration="group=Group%3D-1" label="Files" /><link type="Telligent.Evolution.Ideation.Plugins.GroupIdeasCustomNavigationPlugin, Telligent.Evolution.Ideation" id="c2bcd53b-03ba-4b28-98a1-56d5f125bcee" configuration="groupid=-1" label="Ideas" /><link type="Telligent.Evolution.Calendar.Internal.Controls.CustomNavigation.GroupCalendarsCustomNavigationPlugin, Telligent.Evolution.Calendar" id="00afa562-c814-47d7-9c79-73aca9a0fc09" configuration="group=Group%3D-1" label="Calendars" /><link type="FourRoads.Tickets.Plugins.Navigation.TicketsNavigationPlugin, FourRoads.VerintCommunity.TicketApplication" id="155f13cb-cbb5-4fed-bdde-5cbbd02fe256" configuration="groupid=1002&label=" label="Tickets" /><link type="Telligent.Evolution.Controls.SingleGroupMembersCustomNavigationPlugin, Telligent.Evolution.Platform" id="38d7c7a3-003e-4506-8ffb-6babcd808246" configuration="group=Group%3D-1" label="Members" /><link type="Telligent.Evolution.Controls.SingleGroupMentionsCustomNavigationPlugin, Telligent.Evolution.Platform" id="e8d35e3e-fcda-4a1a-81f6-26aa8d54c966" configuration="group=Group%3D-1" label="Mentions" /><link type="Telligent.Evolution.Controls.SingleGroupSubGroupsCustomNavigationPlugin, Telligent.Evolution.Platform" id="f7f94714-d501-42e0-aa4c-6f8e2da4735e" configuration="group=Group%3D-1" label="Sub-Groups" /><link type="Telligent.Evolution.Controls.SingleGroupTagsCustomNavigationPlugin, Telligent.Evolution.Platform" id="e6f3ad0a-2e0a-4ff2-b685-89e1f470d2c3" configuration="group=Group%3D-1" label="Tags" /></links></navigation>

Finally found the cause if the property Url of CustomNavigationItem is empty then the navigation does not display, which makes sense, however there are no errors or warnings raised to indicate there is an issue. 

Finally found the cause if the property Url of CustomNavigationItem is empty then the navigation does not display, which makes sense, however there are no errors or warnings raised to indicate there is an issue.