Not sure if this is a cache issue or not, but there is an issue which will prevent an application showing up in the Applications Menu.
How to replicate.
Create a new Menu, name it whatever you like as it is important,
In the new Menu, click on New Menu Item,
From the Menus configuration, select Application as type, and select Forum from the Applications.
Click the edit button for the new menu item you just created,
Change the Application to Drawer, and enter a Title (as this is required) and save.
Create a new menu item under the sam